Suunto Smart Heart Rate Belt keeps losing connection to the watch

Calando

Update - factory reset did not help as well, same behavior than before. Pairing the sensor was possible after three tries, starting the training also needed two tries until the sensor was detected. Then the heart rate was measured for some time until the connection dropped. Came back after some minutes, dropped again and so on. In the end, my 5k @ 5.34/km was rated a recovery run. Definitely had nothing to do with strap contacts being too dry (28°C… definitely enough sweat).

Interestingly, also the speed reading is quite “staggered”, this was not the case before the sensor problem occurred (the graph was much smoother).

I saw that speed sampling problem before, though:

And it used to be good for the first few months since I used the Suunto:

Since the strap is brand new, it’s either the sensor itself which does not transmit, or the watch is not able to handle the BT connection. Hard to find out, though, without having an alternative sensor.

Well, I’ll give the watch one more chance using another Sensor (Polar H10), if that also does not help, the watch will be presumably sold (with regret).

Stefano M64

@Calando did you ever paired the Suunto strap with some other device, like the smartphone? A similar behavior happened to me with an headphone which I paired with more devices: it erratically disconnected from one device and connected to another one. I had to clear all the pairing, and re-pair it with one device only.

Calando

@Stefano-M64 No, never paired to anything else. Just talked to Suunto Support, they told me to file an RMA and send the sensor (it’s still inside the guarantee period)

SuperFlo75

I have this problem with the Suunto HR belt since November 2025… I reported this several times here, and I contacted the support… they told me to send logs… it’s a problem with SV1… it’s a problem with SV2… with two different HR belts… and that’s why I don’t think that this is a problem of a belt or a watch… this is a Suunto problem, but it seems that they don’t care about this…

Calando

@SuperFlo75 Just got my new Polar H10. Paired with the Race 2 - works perfectly without any dropouts until now. Will be interesting whether the Suunto Smart Sensor will work as well (again) when returned from Suunto Repair…

LapaS

For me this issue started first time in July last year. Had a probably 1-2y old Suunto sensor and belt. I though the sensor was broken so I bought a completely new set of sensor and belt. Still with the new set the issues continued. I am using Suunto Vertical 1 and Suunto 9 peak for different sports so I was able to test with multiple devices. Both had the same issue with the new sensor. Then the sensor was send to Suunto repair in Czech Republic as it had warranty. Solution was that they replaced my new sensor with another new sensor. That fixed the issue until now. A few days back I started to face the similar issue with both watches. Why it worked well for several months and is now having again the same issue is very strange. And I am also thinking as my device was already replaced with warranty, is there anymore warranty for the replace device? Most likely not.

Calando

@LapaS Correct, for a guarantee-replaced device you get no new guarantee (just the remaining time - 1y guarantee, if you get a replacement after 8 months, the replacement will have 4 months of guarantee).

Try another HR strap - two of my colleagues are using the Polar H10 and never faced any problems (they have Polar and Garmin watches). My H10 also still works perfectly with my Race 2 (see above). Another advantage of the H10 - replacement straps are more than 30% cheaper than the Suunto ones.

In the meantime, I am unfortunately pretty much convinced that @sindavide was correct in his post above.

bubuche

I get the same kind of issue this weekend. The watch connects to the device every minute and then disconnects, ever and ever.
I first suspected the watch (Vertical 1), but the issue also occurs with the Suunto App (iOS) when recording an activity. So looks like a smart belt issue.
I removed the battery for one night, no effect. My previous one lasted much longer than this one (less than two years).

vinc14

reading because i’m thinking about getting Polar H10

LapaS

@Calando said:

@LapaS Correct, for a guarantee-replaced device you get no new guarantee (just the remaining time - 1y guarantee, if you get a replacement after 8 months, the replacement will have 4 months of guarantee).

Try another HR strap - two of my colleagues are using the Polar H10 and never faced any problems (they have Polar and Garmin watches). My H10 also still works perfectly with my Race 2 (see above). Another advantage of the H10 - replacement straps are more than 30% cheaper than the Suunto ones.

In the meantime, I am unfortunately pretty much convinced that @sindavide was correct in his post above.

I asked Suunto about warranty and since my original sensor was bought under a year ago they said warranty should cover the replacement device. So the device is now going to Suunto repair. Anyway my wife had a Polar H10 sensor lying around that had not been used for a while. I bought a new strap for that. At first the sensor was not connecting to anything (phone, watch) but then I saw a discussion on H10 issues where someone suggested putting a small piece of cardboard under the battery (clearly the battery was not touching the connectors). After this connection worked perfectly. Also tested one workout with H10 & Suunto Vertical. Connection worked perfectly throughout the whole session. It would still be good to have also the Suunto sensor working since I need that for workouts where I can’t use a watch.