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:
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:
- At the moment, and whether I should change my pace; and,
- 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.
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.
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