Heart rate monitor troubleshooting: Suunto Smart Sensor & Ambit3 Peak

Last November my heart rate monitor was not working properly. Readings were regularly inconsistent and inaccurate during training runs. I use the Suunto Smart Sensor and Suunto Ambit3 Peak (long-term review), which I purchased together in August and used together without incident for the first 150 hours.

Here is an example of its behavior:

Screenshot from Movescount

The readings are sometimes accurate, like between 8 and 25 minutes, when my HR was in the 130’s during a warm-up.

But more often the readings are not correct. My max HR is about 178, so readings in excess of that threshold (like 200+ bpm for the first 8 minutes and again around 55 minutes) are simply wrong. I’m also skeptical my HR was in the 130’s between 30 and 42 minutes, which were the first 12 minutes of a 30-minute tempo at 5:38 minute/mile pace. More likely, it was in the 150’s or 160’s.

Erratic readings are unacceptable. I need my HRM to be always accurate, so that I know my effort:

  1. At the moment, and whether I should change my pace; and,
  2. Over a given distance or time, i.e. average, so that I can compare workouts from different days, weeks, and years.

Troubleshooting: Suunto Sensor

I tried to reestablish correct readings a multitude of ways until one of them worked. For years I have successfully used a HRM, so it was more than simple user error, such as not:

  • Pairing it correctly to the watch (refer to this video),
  • Wearing it correctly around my chest, at the base of my pectoral muscles,
  • Wetting the electrodes thoroughly before use, or
  • Cleaning it regularly with warm soapy water. (I wash mine daily during my post-run shower.)

1. Battery replacement

The Smart Sensor needs one CR20125 coin cell battery. A weak battery may not reliably receive readings from the electrodes or transmit the data to the watch. This didn’t solve my issue.

2. Leave my phone at home

My problem seemed to arise around the same time that I began to regularly listen to music during my runs using my phone. But on runs without my phone, the problem remained.

3. Re-pair

Wet the HRM, put it on, and re-pair the HRM to the watch.

4. Reset the module

This can be done with the Duel Comfort Belt, but not the Smart Sensor.

Remove the battery. Put it back in, inverted, for 10 seconds. Remove the battery again, and put it back correctly.

The module will need to be re-paired with the watch, per #3.

5. Reset the watch

Before attempting this, download all log data to Movescount. If you reset the watch without downloading the data first, it will be gone forever.

To reset the watch, hold all five buttons (for about 12 seconds) until it resets.

The watch can be partially reset in two ways:

1. Enter the Service menu, by holding the two top buttons (Back Lap and Start/Stop) for 12 seconds. Select “Action” and then “Power Off.” To turn the watch back on, hook it to its USB charger.

2. In your Movescount account, go to “Watches.” Select the option, “Restore default values.”

After resetting the watch, it will need to be re-paired with the Smart Sensor.

6. Contact Suunto customer service

On the Suunto website, there are hundreds of Product FAQ’s. If you can’t find information that solves your problem, call them toll-free at 855-258-0900 (USA).

7. Replace the module or belt

Ultimately, I had to replace the belt.

An entirely new Smart Sensor Belt retails for $80. But a replacement belt costs less, about $30. If your current belt’s electrodes or sensor connectors are damaged, this should solve the problem.

Alternatively, you may have to replace the module, which is more expensive on is own. If your Smart Sensor is not pairing to your watch or if the watch regularly loses the signal, it probably is the module, not the belt.

If your Smart Sensor was purchased from an authorized dealer, it is warrantied for a year. Customer Service should take care of you.

8. Buy an entirely different sensor

A new Smart Sensor belt solves the problem in the short term, but the failure rate has demonstrated to be very high based on the comments in this post and my own first-hand experience.

For a long-term solution, it’s necessary to buy a HRM from another brand. Based on comments, it sounds like the Polar H10 is the most reliable, and it’s fully compatible with the Suunto watches.

Disclosure. I strive to offer field-tested and trustworthy information, insights, and advice. I have no financial affiliations with or interests in any brands or products, and I do not publish sponsored content

This website is supported by affiliate marketing, whereby for referral traffic I receive a small commission from select vendors like Amazon or REI, at no cost to the reader. As an Amazon Associate I earn from qualifying purchases.

Posted in on March 16, 2018


  1. Bob S. on March 16, 2018 at 5:56 pm

    I had the same problem with a Garmin Premium HRM reading over 200 bpm. Replacing the battery didn’t work so I called Garmin and complained. To their credit Garmin sent me a replacement HRM and did not ask for the old one back. I’m not sure if I bought a bad replacement battery or the strap was just messed up and needed washing because I sweat more than the average human but over the years I lost track of which monitor goes with which strap. I was able to rule out the problem was not with my bike computer because I had the same issue with my watch.

    Whatever combination of strap and monitor I’m using now seems to work so I’ll just file it under unsolved mysteries of the universe.

    • Lauri on February 24, 2020 at 10:56 am

      Same here. Tried all the tricks. Does anyone know if the new wathes which measure hr from wrist are any better? Really tired with suunto.

      • Carlton on March 19, 2021 at 5:50 am

        Tired with suunto is a fantastic point!! Back to polar for me. Suunto have consistently useless.????

    • Marc on July 20, 2020 at 8:21 am

      I changes my belt to H10 suunto ambit3 and works a lot better

    • Jeroen on October 20, 2021 at 9:57 am

      Same issue for me, trying to get help from customer service but it’s not really helpful. What’s strange for me is pairing the smart-sensor directly to Strava yields okay results… but through the watch I’m experiencing what you describe above… :/

  2. Jeff D. on March 20, 2018 at 7:55 am

    I had a very similar problem with the Ambit 3 Peak and Suunto Smart Sensor. Both units were purchased in December 2016 and functioned without issue until November/December 2017. The readings would jump from 70s to 200 plus without cause and it never seemed to settle into a pattern. I replaced the battery then replaced the Smart Sensor without any luck. I even tried heart rate sensor gel since it’s winter and I’ve heard static electricity can be an issue. Finally replaced the sensor with a Polar H10 and haven’t had any issues. I’ve used the Ambit and corresponding heart rate monitor religiously since 2012 and this has been my only complaint. Strange.

    • Uri on June 12, 2018 at 8:06 am

      Thanks for sharing Jeff.
      Just to confirm – is Polar H10 compatible with the Ambit 3?
      Does it pair with the watch without any issue?

      • B on July 20, 2018 at 8:38 am

        Hi Uri,

        Did you test the N10 with the Ambit 3?

        • Jeff D. on August 14, 2018 at 11:40 am

          I have not tested the N10 with the Ambit 3.

      • Jeff D. on August 14, 2018 at 11:40 am

        Sorry for the late reply, but yes the Polar H10 does pair with the Ambit 3 without issue.

        • Uri on August 29, 2018 at 1:03 am

          Thanks. Good to know.

    • Ian on December 6, 2018 at 6:02 am

      I’ve had recently the same issue with Ambit 3 and HR sensor. The belt was replaced earlier this year, and suddenly have seen spikes of up to 223bpm, my max is 180bpm and has rarely gone over this. I 100% feel it when/if it has gone over this. reluctant to change belt then sensor especially at an additional cost of £65 for the 2, in case it doesn’t work.
      I’m going to change the battery first to a known brand to see if this works…..Fingers crossed but it is definitely frustrating not knowing if it’s watch/belt/sensor or external factor like other bluetooth devices messing it up.

  3. John M. on March 20, 2018 at 5:57 pm

    This really is a problem with all “soft straps”. They all will fail, from the pricy name brand versions to the generic versions you can find on Amazon. I gave up myself and bought the old style Garmin hard strap, yea it’s not as comfortable but it should last much longer. (and it’s only $25ish now).

    But even then it still will have the erratic heart rates when you first start unless you really slobber over the contacts or use some gel.

    • Fat Old Man on June 3, 2020 at 8:47 am

      I’ve used “soft straps” for maybe 30 yrs, and I’ve never seen anything as bad as this Suunto strap. Mine are dying in less than a year, which is crazy – It’s like subscribing to a $3/mo strap service! I’m going to try the Polar H10+.

      • Larsson on June 3, 2020 at 1:00 pm

        Can highly recommend Polar h10. Had same issues. All problems solved with polar.

      • BobO on July 20, 2020 at 7:36 am

        Did the switch to the H10 work for you? And, which Suunto watch did you pair it with? I have an old Ambit 2, which works fine, but the cost of the replacement strap (which will fail again) is prohibitive.

        • Jeff on July 20, 2020 at 7:58 am

          I’ve used the Polar H10 for years now with both an Ambit 3 and the Suunto 9. No complaints.

      • Alastair on February 5, 2021 at 8:54 pm

        Agree : this is my experience. The strap is BAD, the elastic wears fast and cannot be replaced: only lasted less than 12/12 twice now and the irregular performance is the same on the Suunto 9. USELESS really. I will take the hint and try the Polar strap. I have only had good experience with Polar watches and straps: my straps lasted 15 years WITHOUT battery replacement, but were too old to now replace the battery it seem 🙁 Cheers

  4. Tom on April 10, 2018 at 7:30 am

    Thanks for the comprehensive information. You rock! My heart rate monitor (smart sensor) Ambit3 was doing the same thing as yours was…worked well for many hours and then was randomly showing blank spaces of no reading for long periods of my workouts and inaccurate readings when it did register. Like you I use it to compare workouts and to dial up or down my pace in real time. My fix was reseting the ambit3 with the 12 second solution. Now I have a proper read and don’t have to spend $80 on a new sensor!


  5. L'toi on May 7, 2018 at 7:33 am

    I have a similar problem that only occurs when I am running (not cycling) and also more frequently when I start the run. The reading is WAY too high, but with (what seems) correct variation – it is like an additional 60 bpm is added to my HR. When I cycle I do not have this problem.
    My initial conclusion was that the HRM does not like bouncing up and down – because that is essentially the difference between running and cycling. I adjusted the strap until it was really tight. No joy!
    Then I read that the polyester that my running shirt is made of might produce static electricity that interferes with the HRM. This makes perfect sense and explains why my readings are mostly off at the beginning of my run (because later on I have sweated a bit and my shirt get damp – no static!) and also why I don’t have any problems with cycling (the shirt does not bounce up and down to produce static)

  6. Grambo on July 10, 2018 at 9:48 am

    Suggested alternatives for a HR belt/sensor that will work with the Ambit3? I’ve replaced my Suunto Smart Belt twice, replaced the battery, re-paired, etc., and the reading is still erratic — works great, and then inexplicably cuts out or shows a reading that’s waaaay too high; and then settles down again. Tired of dealing with this, as I use the HR to dial in my easy days and races.

    • Andrew Skurka on July 10, 2018 at 5:01 pm

      If you find one let me know. Any Bluetooth HRM should work. Unfortunately you’ll have to pony up a fair bit to get out of the Suunto ecosystem. I just keep replacing the belts, and that seems to do the trick (for a while).

    • Scott on June 9, 2019 at 1:13 am

      I’ve had great success pairing and using a Wahoo TickR strap and transmitter.

  7. Grambo on July 11, 2018 at 8:05 am

    I’m contacting Suunto. It’s almost like they designed this to mess with our heads, “Let’s make it run totally fine on this run/ride…then cut out…then back to normal…then randomly add 40-60bpm for no reason at all.” Will keep you posted. And thanks for the blog piece on this. I have to believe many Ambit3 owners have run into this, and Suunto ought to address it. It’s not like HR monitors or straps are new tech.

    • Grambo on July 26, 2018 at 12:41 pm

      Update: I just spoke with Suunto customer service and they’re sending me a new sensor. Hoping that resolves the issue, although I’m a little skeptical, as my current Smart Belt/sensor DOES picks up my HR just fine about 90% of any given workout. It just continues to jump or stop reading, ranging from a couple seconds to many minutes with no rhyme, reason or pattern. Seems the only way to resolve issues with Suunto is with a phone call to their toll free number. I originally emailed them receipts for my Ambit3 and my new-ish Smart Belt (took a while to find Suunto’s U.S. email) and got a reply back that I had to call. A small hassle, but they were friendly and quick to offer a replacement sensor.

      • Alastair on February 5, 2021 at 8:56 pm

        They sent me a new one but it failed as well in less that 12 months

  8. Betsy on July 18, 2018 at 8:20 am

    I was glad to read these. Thought I was going to have to visit a cardio doctor !
    I used it for a long time with no problem while rowing paired with CrewNerd app. Changing battery helped some but still some erratic spikes.

  9. Terry on August 6, 2018 at 4:14 pm

    Seems like a common problem. I have the same thing.

  10. Betsy on August 6, 2018 at 5:28 pm

    BlueTooth HR monitor recommended by app. Ordered and retired the Suunto monitor.

  11. Terry on August 6, 2018 at 5:43 pm

    Betsy What did you actually buy?

  12. Betsy on August 6, 2018 at 6:09 pm

    Arriving tomorrow, via Amazon : a generic BlueTooth HR belt. Should pair up better with my CrewNerd rowing app. Will know better on Wed after morning row. For now I have a Fit Bit which does not quite know about rowing nor give the instant feedback. However, it does not show indications that HR is at 210 bpm while at dock before even getting in boat !

  13. Betsy on August 7, 2018 at 3:37 am

    Onlyesh CooSpo H6 Dual Mode Bluetooth & ANT+ Heart Rate Monitor/Bluetooth V4.0 Wireless Sport Heart Rate Sensor Chest Belt Monitor for Real-time Reciever

  14. Christopher Robinson on August 12, 2018 at 12:20 pm

    I recently bought a used Ambit3 and have decided I need a HRM. Confused that the standard strap is medium and even Suunto doesn’t seem to have a larger strap. My chest is in the 40s. Any links to a larger one?

    Betsy, I would love to know how your CooSpo is working out.

    • Betsy Mitchell on August 13, 2018 at 8:37 am

      I have rowed a few times since new HR monitor arrive, replacing the Suunto belt that was erratic. Once I was able to pair with app and phone ( takes patience to be “discovered”), my CrewNerd app worked great. I compared it to the Fitbit while doing a piece and found that over 90bpm, the Fitbit was less dependable than the (Amazon) CooSpo HRM.
      Once paired , it automatically displayed info with the app.
      Happy for now.

    • Bob S. on August 13, 2018 at 2:02 pm

      Christopher,I have the same problem with my Garmin chest strap; If I gain 2 more pounds I’ll need a bra extender. Personally, I think chest straps are uncomfortable so I set the optical sensor on my Garmin watch to broadcast heartrate data to my bicycle computer. Maybe it’s not the most accurate way to monitor heartrate for a professional athlete but it works well enough for my needs.

      I don’t think I have ever seen Andrew weigh in on dedicated optical forearm band HRMs vs chest straps so if anyone has tried one I’d be curious to know how well they work.

  15. Jeff D. on August 14, 2018 at 11:45 am

    After having the same issue with both the Suunto Smart Sensor and the Polar H10 (which pairs to the Ambit 3), I came across the article below on thoroughly washing the strap. Apparently, hand washing the strap wasn’t removing all of the body oils because it’s worked flawlessly after a comprehensive wash. It’s free, so worth trying before spending the money.


    • Michael Sharp on November 19, 2019 at 10:48 am

      Everything that everyone said about the weird characteristic of the Ambit 3 Peak & Suunto HR chest-band monitor was my experience too.

      I think following the essence of natharwards link (post 14Aug18) has worked!

      As it happened, out of frustration, I’d ordered a third band since buying the watch/HR in Feb17 (& I’m on my second sensor – all because of the spurious HR recording) at the same time as a spate of chronic ‘nonsense’ results.

      So I used the new belt with old sensor – no problems (yey!)

      So I washed the old belt in our washing machine (40degC ca 40min cycle) and then cleaned the plastic skin sensors with 70% solution of Isopropanol – (aka rubbing alcohol – 500ml ca GBP6 on amazon) and wiped away any excess.
      Out for a run today – old belt old sensor – no problems (double yey!)

      Before rubbing alcohol / washing machine treatment, old belt old sensor was coming back with 220+’s and prolonged 170+ when running at ‘active recovery pace’. However, I was only washing the belt, probably less than thoroughly than necessary, during my post-run shower.

      …added this comment because this site ‘gave me hope’ & that I was not alone. Hope this helps (I was just a couple of clicks away from buying a Polar N10)

  16. stephanrunning on August 14, 2018 at 1:41 pm

    Thank you very much for this blog post and the very helpful comments. I had exactly the same issue of completely implausible readings. Inspired byJeff D, I started using the Polar N10 in May. This has worked almost perfectly (only a very few temporary drops in the heart rate mostly at the beginning of some workouts).
    After reviewing my data, Suunto Support advised to buy a new belt. Since they had already sent me a new one only a few months before (in January) I decided to switch to the Polar. By the way, I don’t find the N10 less comfortable than the Suunto smart belt which is a little lighter. Hopefully this solution lasts for a while.

  17. Terry on August 15, 2018 at 11:38 pm

    Unlikely as it sounded, I tried the comprehensive wash described above and my HRM has been functioning perfectly ever since. So it’s worth a go.

  18. marc on August 23, 2018 at 1:08 am


    Thanks for sharing… had exactly the same issues… finally hearbeat was not detected anymore and showing faulty on watch alternate… not accurate at all.
    Resetted the watch 12sec and problem solved.

  19. Andrea on September 6, 2018 at 1:21 am

    Thanks for helpful infos, I have same problema, but I’m a little bit skeptical about solutions proposed.

    First: mu Suunto Smart Sensor works perfectly recording the activity with cell and Suunto app: no peak no hole… the heartbeat of a man not an humming-bird!

    Second: also the barometric reading are fuzzy: storm fake-alarms and altitude graph with jumps of hundreds of meters

    I’m going to try with a different bluetooth belt…. Hope never die!

  20. ove on September 21, 2018 at 4:24 am

    Hade the same problem yesterday when running – seemed like adding 60 beats to my HR. Reading on Ambit3 watch read 200-215 beats.
    When I downloaded the run and looked on movescount it seemed to correct the numbers to what looked like normal HR. Anyone know what is up with that? Does movescount have an algorithm that corrects HR?

    • hunter on February 11, 2019 at 9:49 am

      #Ove: yes, somewhere in the past they seem to use a correction software,
      it wasn’t some years ago, but recently they correct.

      But what is better to believe now:
      * the accurate device like Ambit3?
      * the software which is interpolating the source data?
      (if the mistakes are not that obvious, the choice isn’t easy!)

      what I complain now is:
      * no information from SUUNTO on that HR-sensor topic (I’m active with this issue since
      2015, and all I found was from people like you, nothing official.
      * no information on software changes (all you get is ~… “minor changes”, but no details).
      Neither Ambit peak, nor movesLink2, nor movescount (app and/or internet)
      * with every “update” your compatibity with 3rd party Software (like SportsTrack,
      MyTourbook,..) is gone (and these 3rd party acitivies do a great job, but it is hard
      for them to follow, SUUNTOs changes – to be on track
      * if it happend that you forgot your watch at home and tracked somehow else, how to get
      that data into the internet(movescount)? (there was an mxAcivityMover , but I didn’t
      get it working lately (and it was difficult in the past anyway, cause SUUNTOs tricky
      changes all the time).

  21. Dexter on October 11, 2018 at 9:56 pm

    My readings were getting erratic over the last 3 or 4 uses. It would either be low (50-60’s) during exercise or “–“. It paired fine, and I tried all of the other remedies short of purchasing a new strap. I washed it and it works again. Brilliant!

    • Dexter on October 18, 2018 at 9:24 am

      Update to my post on Oct 11th. The cleaning did not correct my problem. It did initially find the HR monitor better but the readings did not improve in consistency. After a little more inspection of my HR monitor I noticed that the battery was not secured properly inside. It wiggled around inside of the monitor and therefore would lose connection which was causing my problem. I removed the battery and bent the 4 connections that hold the battery in place in a little bit which firmly secured the battery again. Vioala! HR monitor connected immediately and recorded perfectly this morning.

      • Dexter on December 6, 2018 at 1:14 pm

        Update on 12/6/18: Despite the cleaning and resecuring the battery clips, I still continue to have issues with the HR monitor. I find that it regularly will not connect as it should.To remedy the situation, I have to remove the battery from the monitor, reinsert it, re-pair it to the watch then it will work as it should. The problem is that it loses its pairing almost after every day that I use it. Not sure what the root problem is. Wish it could be fixed. Not really wanting to buy another one.

  22. Betsy M on October 18, 2018 at 9:51 am

    Good to know. Thanks

  23. Grambo on December 6, 2018 at 12:11 pm

    Update: A new sensor resolved the issue. Phew!
    It took a while to get through to customer service and to have them send a new sensor, but it was worth the hassle. My watch’s HR readings have worked flawlessly since.
    The few times it dropped the signal were almost surely because my skin was too dry starting out on a run or ride.
    Hope that helps. Good luck, everyone, and enjoy a great, outdoorsy winter.

  24. Hussein on December 28, 2018 at 8:02 am

    happy to read I am not the only one having those trouble with HR & ambit 3.
    Suunto is sending me a new sensor/belt for the second time …
    I am still owning my ambit2 (I am still using it) where I had troubles too but only the 10mn of my activity (running only). Thanks for your posts.

  25. Urig on January 2, 2019 at 2:30 am

    Sadly I was also provided with a new sensor and strap, and they worked fine for about two months. Now this set is completely off – showing bad readings throughout long runs (beyond 90 minutes).
    Cleaning, battery replacement etc. do not help.
    Sorry – this is a sub-par product.
    I have decided to purchase a 3rd party HR sensor as I don’t believe Suunto has a real solution.

    • Andrew Skurka on January 2, 2019 at 2:18 pm

      Suunto’s “solution” has been to send replacement units. But that’s a band-aid, not a fix.

      I’m going to ping my Suunto media contact to see if you knows of anything in the works.

    • Urig on January 12, 2019 at 5:05 am

      Purchased a polar H10 sensor. Works perfectly with Ambit3 sport.
      Problem solved.

    • Grambo on January 15, 2019 at 8:09 am

      Yup, exact same situation here. My Suunto replacement sensor/strap worked beautifully for a couple months. Now, it’s as irratic as the one it replaced. Frustrating. Guessing it’s just a bad design that wasn’t thoroughly tested in the real world before Suunto put it on the market. Too bad, because, for me, the failure of this one accessory hurts the reputation of an otherwise great watch (mine is the Ambit Peak3) and great company.
      Not sure what I’ll do now. Probably buy a Polar H7 or H10.

  26. John Payne on January 2, 2019 at 6:15 pm

    Same problem, but I’ve been using the Suunto sensor with the MoveSense app on an iPhone that I carry in my hand. Mine has also been erratic — almost always swings wildly at the beginning of a run, even if I get the strap wet. It seems to stabilize once my skin is a little bit sweaty, but it has also stopped working in the middle of a run, then worked again afterwards. The app has lost my data several times, too. It’s not the battery. I think it’s a combination of imperfect connections between the device, the strap, the athlete’s skin, and bad software and/or hardware that doesn’t react well to those connection problems.

  27. Grambo on January 15, 2019 at 8:10 am

    Yup, exact same situation here. My Suunto replacement sensor/strap worked beautifully for a couple months. Now, it’s as irratic as the one it replaced. Frustrating. Guessing it’s just a bad design that wasn’t thoroughly tested in the real world before Suunto put it on the market. Too bad, because, for me, the failure of this one accessory hurts the reputation of an otherwise great watch (mine is the Ambit Peak3) and great company.
    Not sure what I’ll do now. Probably buy a Polar H7 or H10.

  28. Michał on February 10, 2019 at 5:29 am

    How do you pair your sensor with your mobile using the new Suunto App (not Movescount)?

    • tgwowgt on February 11, 2019 at 3:37 am

      Nothing different. The new Suunto app is the Sport Tracker app with a different logo and a direct link to Suunto watches…

  29. David on February 11, 2019 at 3:55 pm

    Hahaha OMG I wish I read this before.
    I actually believed my HR was going over 200 and had an exercise stress test at the heart clinic.
    Oh well.

  30. Terry Dixon on February 11, 2019 at 4:48 pm

    After persevering with two Suunto HRM’s both which exhibited spurious erratic behaviour I’ve given up and purchased a Polar H10 HRM. So far it has not missed a beat. Hopefully, this solves the problem.

    • hussein on February 15, 2019 at 2:28 am

      Hi Terry, I did the same. Polar H10 super accurate (baught with Polar V650). Not good for suunto I now have a foot in Polar eco-system !and their eco system fit me well.

  31. David on February 15, 2019 at 4:12 am

    1. I found out that wearing the belt tight to the body greatly improves the inconsistent reading, but does not solve it.
    2. I checked previous workout logs & noticed that I’ve had inconsistent reading problem since the day I purchased the watch! I know, very stupid of me not to take care of this while on warranty.

    I was very happy with Suunto besides this problem, but I will not purchase a Suunto ever again.

    • hussein on February 15, 2019 at 4:20 am

      I used the warranty twice and nothing has changed !

  32. PP on February 22, 2019 at 4:55 am

    Hi all,

    nice to know not being the only ones with similar issues. I’ve got my third belt and module within warranty today from Suunto and here’s hoping the spikes in HR will go away. My spouses clock has the same problems and they were bought at the same time.

    My first belt worked for couple of months but had to replace it because of the spikes and the with replacement the same thing after a couple of months.

    I was going to put this latest one due to the cold weather/not wet enough/technical shirt issue, but now I managed to get 248 HR during a very chill run indoors so decided to complain again. Oddly enough, while skiing, the readings are accurate and no spikes in HR…?

    Also (a bit OT), Movescount website and Suunto App gives very different readings for exercises which is quite annoying, but the service guy said it’s because they are developed by different people/a company and that the SA cleans the data differently which why the graphs differ. Even the average HR can be 10-15 beats off comparing MC and SA together. He said to trust the MC website graphs but this seems weird as they are getting rid of it eventually.

    If the Polar H10 is the solution I might go for to it, but fortunately I still got the warranty to keep changing these belts and modules until the fall…

    Cheers for everyone sharing their experiences, this is a small thing in the greater scheme of things, but still very frustrating!

  33. Ceasear on February 25, 2019 at 11:58 pm

    I have similar stiuation. I am using suunto spartan sport and suunto smart sensor for couple of months. At first, it was really ok.. but 2 week ago I camped in forest while the weather was very cold. I went for a run while camping. It was a hard run and I ran with high bpm which generally I am not. Then I put sensor and belt to a plastic refrigirator bag and leave it in a car. Then I came back to home and go for a run and saw that the sensor lost all of it’s accuracy. It shows 135 bpm and suddenly goes 145 and it goes up to 152 despite I start walking.. and suddenly shows 129.. It is frustrating.

    I thought that there is a problem in battery because of cold weather or the plastic bag.. I changed the battery, paired the sensor and try again. It started well but after a 45 50 minutes of run it became silly again and did the same think.

    I am gonna wash the belt, replace the battery again (and first put its back for recharge) and pair it again. I hope these will work.

  34. David on March 15, 2019 at 6:04 pm

    I had an issue of the heart rate reading stopping a few times during runs, creating multiple “black spots” without HR reading with each run (I usually run for 1 hour). Lately, a problem of sudden crazy high HR readings added up.
    I tried the solutions suggested here and nothing helped.
    I contacted Suunto customer service and they offered me nothing but purchasing a new belt since my belt is out of warranty. They offered a discount but then said “oops sorry” when I told them where live (non US/Canada).
    These are the steps I took and now the problem is 100 solved!!!
    I don’t know if this will work for you, but why not try?
    Anyway, it is stupid that Suunto customer service do not suggest these steps to their customers and that I had to find them out by myself:
    1. Replace the battery. Make sure to use the correct type.
    2. Reduce the belt size so the it fits tightly right under your chest. It should NOT be comfortable, it should be tight (but don’t kill yourself).
    3. Wet the 2 black pads on the belt (those that touch your skin) with plenty of water immediately before wearing the belt, ON BOTH OF THEIR SIDES.

    After taking all these steps I made 2 runs and problem is completely SOLVED.
    No drops in reading, No erratic reading. Good as new.
    Please update if you tried my solution and it helped!

  35. Terry Dixon on March 15, 2019 at 6:57 pm

    I tried all those steps and several more. I even acquired a second Suunto HRM. In all cases the problem went away briefly but always returned. Finally, in frustration, I purchased a Polar H10. I have been using the H10 for about 2 months now and have not had a single problem.

    • David on March 15, 2019 at 7:05 pm

      Oh well.. In that case I assume the problem might come back soon 🙁
      If it does come back, I will update here.
      I just read somewhere that the Suunto ANT+ belts require very frequent cleaning. Maybe it needs constant washing in the laundry machine, like once every 3 runs.
      I also just read that many people lick the pads on their HR belts before wearing (seriously) and some even use gel, especially in winter (gel is mentioned in the comments here above somewhere).
      As long as my Suunto watch works I will keep using it, but the next one I purchase will definitely not be a Suunto again.

    • hussein on March 16, 2019 at 9:10 am

      Terry +1 I did the same.

  36. loopylou on March 19, 2019 at 7:45 pm

    I have gone through at least 4 belts/sensors!! Using the Suunto smart sensor chest strap. they have worked for longer if I take the module off the belt after every run and wipe it dry. That makes it last maybe an extra month before it goes erratic again. I have done the clean (worked for a while then the same issues and the clean did not work). I am thinking about buying a different strap now – does the Polar work with Suunto 9? Yes, that has a wrist HR but that is pretty erratic also!

  37. Triathlete on April 17, 2019 at 11:57 pm

    Thanks for this very helpful hint. As an owner of a Suunto Spartan the HR module experience has been very frustrating in the last two years. Sometimes the HR module works, sometimes it shows a HR of 230, sometimes of 30, when actually it is 130-160. Sometimes it connects before the exercise and then after I start the exercise the HR module disconnects and never connects again showing “–” rate. This is not rocket science, is a technology known for decades from Polar and my expectation is that an otherwise good product should have it figured out at launch time.
    What finally worked for me is:
    -I bought a Polar H10 HR belt. Polar have been the leader in the HR watches field for decades. H10 is “the most precise HR belt Polar has ever built” and this is a statement, even if no data is provided. The belt connects immediately when I go into exercise mode (Suunto HR belt takes a minute or never connects)
    -still after starting the exercise, the connection got lost and I saw “–” as HR. I had also updated to the newest software version 2.5.18 some time ago, where apparently the issue has been fixed (“HR belt connection reliability improved when starting exercise” after release 1.12.36 from January 2018). Here the 12 sec software reset helped. Still after starting the exercise the connection to the HR module gets lost for some seconds but then gets rebuilt (which is strange but works).
    Finally, I bought this watch because at that time it was the best on paper for triathlon and mountaineering. For the same purpose, I will consider also Garmin next time I need a new watch. The HR module is not the strength of Suunto Spartan. Garmin also provides a well readable map on some of their watches, which can be an advantage in some situations.

  38. Marshall on May 14, 2019 at 11:55 am

    So am I reading that the Ambit 3 can be paired with a different heart rate monitor & strap? I love my Suunto Ambit 3 and don’t want to give it up but I can’t find a replacement monitor/strap on the web.

    • Andrew Skurka on May 16, 2019 at 8:31 am

      Yes. It must be bluetooth compatible.

      • Grambo on May 16, 2019 at 9:56 am

        I bought a Polar H10 HR strap ($80) a few months ago after lots and lots of frustration trying to get Suunto’s HR strap to work as advertised (including getting a Suunto replacement strap, replacing the batteries and trying every suggestion imaginable for getting it to work consistently).
        The H10 has worked flawlessly with my Ambit3 since. The H7, which is cheaper, would also work, as should any other bluetooth compatible strap.

        Likewise, I really like my Ambit3 Peak watch. But my experience with Suunto’s HR monitor has me thinking I’ll switch to Polar or Garmin when it comes time to replace it.

        • hussein on May 17, 2019 at 7:07 am

          exactly what I did and what I think. They should supply the H10 with Suunto watch, we will all save time & money.

  39. Marshall on May 16, 2019 at 2:59 pm

    Thanks everyone! Awesome news and very helpful 🙂

  40. John Warner on May 30, 2019 at 11:44 am

    Thanks to everyone on this thread. Now I know I’m not alone with the exact same issues.

  41. PP on June 9, 2019 at 7:36 am

    After four belts and two modules (x 2 as my spouse has had the same issues), I finally decided not to fight this anymore and got the Polar H10. As you may guess, paired instantly and no problems with the HR. Last easy run with Suunto belt gave 195 bpm for 10 minutes so I decided to invest in Polar and not get new belts again and again from Suunto Service.

    They replied when I complained about the belts and gave the usual “check the battery”, “make sure the belt is wet”, “pair the module with your watch” jargon but needless to say these hints we all already know and they don’t tackle the issue that their new belts are completely useless after a few months.

    I am going to give feedback to Suunto about their belts and recommend everyone with these problems do the same.

  42. Arild on June 16, 2019 at 2:16 pm

    Thanks to everyone on this thread. I’ve been using the Suunto HR strap with Baro 9 in the last 7-8 months. The last month or so, I’ve experienced the same problems as described here.
    Very helpful, thanks!

  43. Bert on June 26, 2019 at 3:20 am

    Great tips given here! I had similar trouble with the HR belt. Turns out I only need to replace the strap. Resetting the watch and repairing worked. Appreciate the help!

  44. André Martins on August 25, 2019 at 2:51 pm

    Hi everyone. First of all, thanks for the post and the comments. I have an Ambit2 origianl (the big battery one) with the Suunto Heart Strap ANT (the Ambit2 HR combo). I started last week having erroneous readings with Suunto Heart Strap ANT (not the ANT+ version).

    Walking fast the error seems to be 5% to 10%, but it was enough to start running that my pulse, usually between 140-150 bpm jumped to 171, 175, 189bpm… Anyway, someone here commented that he had these same problems using his smartphone and Bluetooth headsets to listen to music. Well, I was again running and listening to music on the phone (JBL Pulse Escape Bluetooth phone and Samsung S9+) and I was having erratic readings. I remembered this, turned off the Bluetooth on the phone, turned off the headphone and, bingo! At this exact moment, the reading of the heartbeat became what it was before.

    I didn’t have this problem before, listening to music on S9+ and running with Ambit2. I don’t know what’s changed, whether it’s changed something or just an erratic reading behavior. However, my intuition believes that this does not have much to do with the clock, be it Ambit2, Ambit3, Peak or another model, but with reading the ANT strap. Does this problem happen with ANT+ straps as well? Thanks for the comments, very useful!

  45. Testa Andrea on January 17, 2020 at 7:40 am

    After some time, I’m having the same problem with Polar belt!

  46. Michael Sharp on January 17, 2020 at 10:02 am

    Posted a comment a bit back that I thought I’d sorted the Suunto HR problem by cleaning it with alcohol etc etc… Wrong! 🙁

    …silly HR data again.

    So I’ve abandoned the Suunto HR (after about 3 yrs trying to make it reliable) and bought the Polar H10 HR. Had it a couple of weeks and working perfectly. Long may it continue 🙂

    Interestingly, the ‘body-side’ sensors on the Suunto belt are two patches about 4″ each. The Polar belt has what appears to be a continuous strip (the width of the belt) that almost goes side-to-side across the chest. Wonder if this is significant?

    • Testa Andrea on January 18, 2020 at 12:57 am

      I Hope for you but in my case also the Polar H10 fails. We have a particolar skin type? I can’t believe that it’s impossible to have a well working belt

  47. Ivana on February 20, 2020 at 3:57 am

    Same issue with the smart sensor and Ambit Peak 3, loosing connection, super high HR etc. al the same same same. Did the battery, the cleaning the wetting…and finally ordered Polar H10, should pick it up tomorrow and test it #fingerscrossed. Suunto really disappointed on this one

  48. tvcrider on April 10, 2020 at 12:54 pm

    I came across this thread last October. I have had nothing, but long-term problems with my Ambit3 Peak and Smart Sensor maintaining a reliable connection and accurate HR. I was often seeing either zero displayed or 60-80 beats above my theoretical maximum! I tried washing the Smart Sensor strap in Dawn dish soap, but connectivity with my Ambit3 was only maintained for a day or two. I didn’t want to drop nearly $90 on the Polar H10, but I finally broke down and purchased one. I have not regretted it.
    I started using the A10 on November 24, 2019. Wow, what a difference! As of today I have had 108 workout sessions since then including: cycling, walking, hiking, and rowing (indoor C2 Ergometer). I have only seen glitchy heart rate readings once since switching to the A10 and honestly I am not sure why? The Polar H10 has working reliability over 99% of the time for me. I rise the belt after every working and once/month I wash it in Dawn soap. I just wish I had come across this blog earlier. Thank you.

  49. Grambo on April 10, 2020 at 2:16 pm

    Glad to hear the thread has been helpful. Similar experience here and my Polar H10 has worked flawlessly with my Ambit 3 Peak for about a year now. Also syncs with my phone easily and quickly. One tip that will help your battery last longer is to remove the sensor from the strap after each use. Doesn’t seem picky about washing, either — I usually just rinse it under cold water and sometimes go a week or so without that. Good luck with your training and adventures!

    • Larsson on May 4, 2020 at 9:36 pm

      I had exact same problem with my Ambit 3. Tried everything without results. Buying a new Polar H10 belt finally solved the issue.

  50. Johnit on April 11, 2020 at 5:56 am

    I have seen the same problems with the Smart Sensor and belt – three belts and two sensors later. Wahoo sensors did not last either. I now have a Gamin Fenix 5X and the Garmin belts have never lasted me longer than a year. Polar belts are compatible with the Garmin sensors and in my case, they last at least three years. So between all the above, the Polar belt and H10 sensor will work with almost all training watches.

    • hussein on May 5, 2020 at 7:06 am

      I have both Polar H10 and Polar OH1 and both do a perfect job for me.

  51. Viking79 on May 4, 2020 at 2:03 am

    I have exactly the same problems with my Suunto Spartan. Mostly while running, it seems. Not cycling or cross-country skiing. Sometimes it starts at 200 bpm from the first meter, then stabilizes. And sometimes, it just goes wild, and gradually rises by 30-60 bpm in the middle of a workout. Looks like I have some kind of heart condition. This happened today. I was focusing on keeping under 132 bpm in a Z2 run up a hill. When finally on top at around 127, being careful to not speed up too much on a flat, the watch suddenly showed 135, 140, 150.. I almost stopped, and held my finger against the side of my neck, but could nearly count the beats, the pulse was quite weak and probably down to almost 100 bpm by this point, anyways I counted 36 in 20 secs, X3 = 108, so that makes sense, but the watch showed 157 or something. I think it even said 168 at one point. I detached one of the buttons, figuring I didn’t want to use hr data for the rest of the run. I noticed it didn’t seem to stop recording, so I thought I’d just as well attach the button again. After a short while, the pulse seemed normal again. And that lasted for the rest of the 7 km. run.

    Now the strangest thing, that I don’t think I’ve seen before: The behavior I just described doesn’t show in the Movescounts app or in Strava. The pulse there is hovring around 115-130 just as it should, except where it went wild and slowed down, there it drops gradually towards 100 as I slowed down the pace severely, until I detached the strap, where it shows 0. Then it picks up again at around 110 which is probably correct. I remember it said 113 bpm and it felt like that. Have Suunto corrected the algorithms used by Movescount or something?

    I wear the belt tight and wet the sensors properly, but no it doesn’t help. I was suspecting the battery.. I have a Wahoo TickrX and a Garmin Edge belt, will try that.

  52. BobO on July 20, 2020 at 7:50 am

    Hi all, just stumbled on this thread. Great info and sharing of! I have an ancient Ambit 2, have had good enough luck with the HR readings, but I keep breaking the belt where it intersects with the monitor. I haven’t seen anyone comment about the compatability of the Polar H10 with an Ambit 2. Would they work together?

    • Hussein on July 20, 2020 at 10:15 am

      I confirm Ambit 2 and Polar H10 work perfectly together. Same for OH1 and Ambit 2 too !

      • BobO on July 22, 2020 at 7:14 am

        Thank you! I didn’t relish the notion of purchasing a new watch, just for the HR belt.

    • johnit on July 21, 2020 at 11:12 pm

      The Polar H10 as well as the H9 will work – they support the Ant+ protocol which the Ambit 2 uses. In my experience the Polar belts last long – a lot better than other brands. The H9 costs less than the H10; the main difference being that the H10 has memory and can record without a watch, whereas the H9 has no memory. Treat the belts well by washing after use as per Polar instructions, and be careful in unclipping the sensor from the belt to minimise stress on the belt.

      • BobO on July 22, 2020 at 7:16 am

        Thank you! Good tip on the H9.
        The watch has served me well, and I didn’t look forward to buying a new one just for HR capability.

  53. Emal on July 20, 2020 at 9:28 am

    Same problem with Suunto Spartan Ultra. New belt, new battery and still have problem. HR over 200 when I start training. I think it is time for Polar.

  54. Lize Theron on November 1, 2020 at 12:27 am

    Do I need to re-pair my monitor and watch after a long lay off. My watch cant find my HRM -SUUNTO

  55. Grambo on November 1, 2020 at 4:22 pm

    It’s worth trying. Also, check your HR monitor battery. They can drain faster than one might expect, especially if the pod is always attached to the strap. I’ve found the battery life is much better with the Polar H10 than with the Suunto HR monitor. Still like my Ambit3 Peak a lot, though, and don’t feel any need to upgrade.

  56. Lize on November 1, 2020 at 8:56 pm


  57. Andrew on February 10, 2021 at 3:55 am

    Hi, I have just recently bought the Polar OH1 to pair with my Ambit Peak 3. It works really well during exercise, whatever the type. But it fails to pair if I want to run the ‘recovery’ tests. I’ve tried resetting the watch, re-pairing, I’ve even tried it directly after exercising when the connection with the OH1 was good. The watch says turn on HR belt and relax, then a screen about searching for the belt appears before a ‘failure’ alert plays and the watch goes back to the ‘recovery’ screen. I thought my HR is low, but not THAT low that it doesn’t pick up at all! 🙂 Thanks in advance for any wisdom.

    • Andrew Skurka on February 10, 2021 at 6:00 pm

      Stumped, sorry. I didn’t even know what the “recovery” mode is…

      • Andrew on February 10, 2021 at 10:25 pm

        Me neither! I’ve had the Ambit 2 for a few years and now the Ambit 3 for a year and only just yesterday found the Recovery screen in the Start/Stop menu (after I had paired the OH1). Got excited about it, but seems that was short lived! 🙂

    • Grambo on March 19, 2021 at 8:38 am

      I do run the recovery test on my Ambit3 Peak now and then, both the quick test and sleep test. It basically confirms how recovered I’m actually feeling, based on decades of doing endurance sports: still not recovered from a long/hard effort (even if I think I should be); ready to go harder than I might think; stressed from long work hours and too little sleep, etc.
      Sorry I can’t help with your pairing issue, but if your HR strap/monitor is bluetooth compatible, you might also try pairing it with your phone and using an HRV (heart rate variability) app. That should give you similar results on where you’re at recovery wise.
      HRV is based on research that shows the time between each individual heartbeat varies based on how well recovered you are (this is not the same as beats per minutes, which some athletes measure each morning on waking to see if they’re recovered).
      The HRV data can be a little overwhelming, so most watches will just say what percent recovered you are, or (like the Suunto) say how many hours you have to be fully recovered.
      In any case, I don’t use HRV or the recovery mode on my watch all that much (maybe a couple weeks throughout the year) because I’ve found it just confirms what I’m already feeling on any given day — too old and lots slower to recover than when I was a kid!

  58. tvcrider on March 19, 2021 at 9:55 am

    I’ve been successfully using the Polar H10 belt paired with my Suunto Ambit3 since November 2019 with very reliable results. After 14+ months (Feb 2021) the heart rate pick-up/transmission finally became very spotty again. I checked the output of the installed 2032 battery (3V) with a voltmeter. When new the 2032 batteries will pump out roughly 3.2 volts. Mine had dropped to 2.6 volts. I installed a new battery. Problem solved.
    Fwiw: I do normally pull the heart rate sensor from the belt between workouts; rinse the belt after every session; and wash the belt roughly once/week.

  59. Olli Salonen on April 19, 2021 at 2:01 am

    I like the watch, but the Smart Sensor sucks indeed. I observed exactly same behaviour as Andrew described here after a year of use. Suunto recommended buying a new belt as replacement. Replaced the Smart Sensor with Polar H10 instead.

  60. Matt on June 22, 2021 at 10:07 am

    Hi appreciate this thread, i just got a H10 for my Ambit3 Peak and it will pair with the Polar Beat app as well as the watch, but when i enter an activity no HR shows up on the watch. Does anyone have a solution for this? For example, pair HR belt, enter activity, HR belt found. then when I go to a screen with a HR the bmp is just “–”

    Also, do i need to pair the HR strap with the Ambit3 every time i want to use it? My watch does not seem to find the H10 automatically like it did with the SmartSensor. not a deal breaker but wonder if something is wrong with my watch.

    • Matt on June 22, 2021 at 10:17 am

      MOD – i did a soft reset again and it seems to be working now. feel free to delete my post

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  62. Mark R. on April 26, 2022 at 2:01 pm

    I got ambit2s and hrm chest strap. The strap stopped pairing. I did step 4 and then re-paired hrm with watch and it worked. Thank you very much, excellent guide..

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