Suunto Smart Heart Rate Belt keeps losing connection to the watch
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@JaakkoK
I have recently experinced tha same issue with a smart belt bought in february. Lately short disconnections occurred, which had never happened before. Lastly, on Sunday after a couple of short dicinnections, the belt and the watch never reconnected for the rest of the workout. After the end of the session, i restarted another one and the watch saw the sensor without issues. Nevertheless, Given that in 10 years i have replaced several sensors because faulty or dead, i attribute this to the sensor, not the watch. Fiven that i bought it on amazon, i returned it and bought a new one, so let’s see.
The suunto smart sensor is not exactly a piece of reliable engineering, actually is quite crap, as i said i replaced several of them, i guess some 5 or 6 since 2015 -
@sindavide I’m also almost sure the the issue I have it’s a faulty Suunto Chest Strap. The Suunto Run is behaving awesomely for me in any other respect.
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I don’t have a Suunto chest strap.
I think the problem with mine is a combination of my stryd and a polar oh1+ (although I think the heart rate sensor is irrelevant)
The stryd causes some odd behavior when I do warmup exercises at my athletics club. While doing planks, my watch buzzes due to some signal from my stryd (is my assumption, the buzz is real, the cause is assuming) and after that my watch loses connection to my heart rate sensor.
Last couple of weeks we didn’t do that kind of exercises and I had no problem with disconnecting heart rate sensor.
I suspect the problem is in the watch firmware. It either cannot handle certain signals from my stryd or it cannot deal with disconnecting sensors.
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Same problem here, Suunto Smart Sensor connected to a Race 2. Worked flawlessly for seven months until last Sunday when suddenly the sensor connection dropped after starting the run. First idea was of course the battery, inserted a new one, problem remained. Chest strap is always washed after training, bought a new one anyway, problem remained.
I measured the resistance of the brand new strap and the older one; new one has approx. 1.38 kOhms (2x700 ohms), older one has 2.85 kOhms (2x1.43 kOhms), but up to now I heard that the straps should be good if they are below 8-10 kOhms.
Warm reset of the watch did not help, re-pairing the sensor did not help as well. I have no idea why that happens; the last firmware update of the Race 2 was beginning of April, and the watch performed without any hiccup afterwards.
I did a factory reset last night, will try again this evening whether that helped. Also bought a Polar H10 as backup solution… so that sensor problem cost me more than 100 EUR up to now (btw, 39 EUR for a replacement strap is much more expensive than Polar, they sell replacement straps for 25 EUR).
Suunto wants to sell the Race 2 as a training device for runners - training without a reliable HR detection is no option, though. I do not want to use OHR as well, it’s usually quite a few beats off if I am not just sitting at a desk.
Any other ideas except for “the suunto smart sensor is not exactly a piece of reliable engineering, actually is quite crap”?
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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).
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@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.
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@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)
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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…
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@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…
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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.
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@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.
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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). -
reading because i’m thinking about getting Polar H10
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@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.
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A special price combination between the Suunto Vertical 2 and the Coospo HW9 creates a high-level set with excellent value for money. You get maximum reliability in reading your workouts without having to spend a fortune on sensors from more expensive brands. I explain why this pair works so well and what guarantees the accuracy you are looking for: Why this pair is reliable. Arm Optical Sensor Accuracy: The Coospo HW9 uses a modern optical sensor that detects blood flow in the forearm or bicep. It is a region with much less interference from sudden movements and tremors than the wrist, which eliminates those “peaks” or false drops in heart rate. Shooting Reading Speed (Intervals): While the wrist sensors of any watch suffer from a delay (lag) in understanding that your intensity has increased in shooting workouts, the HW9 responds almost in real time. It is the closest you will get to the accuracy of a chest strap, but with the comfort of a wristband. Supreme Battery Savings: The Suunto Vertical 2 is already famous for its monstrous battery. When pairing the Coospo HW9, the watch turns off the rear green wrist reading LEDs. This drastically reduces the watch’s energy consumption during workouts, further extending its battery life on trails and ultras.
Suunto’s Bluetooth protocol talks very well with Coospo chips. Once paired, the chance of signal drop during the run is practically zero.
I used Polar for a long time and I don’t spend with them anymore.
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@elbee
Could the watch firmware. I never had any issues before the last update.
By the way, i got a new suunto smart sensor, and it occasionally dosconnecta - the watch does not show hr - albeit for not long -
@Marcelo-Mönch Does this work with the Suunto ZoneSense? I think that ZoneSense requires a chest strap since it needs HRV data which cannot be provided reliably from an OHR !?
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@Calando Why is a chest strap necessary? Beat-by-beat data: ZoneSense uses a proprietary physiological algorithm (DDFA) that analyzes Heart Rate Variability (HRV) to determine stress and intensity levels.
Optical limitations: Optical sensors (OHR) cannot reliably measure RR intervals (the exact time between heartbeats) while you are in motion. They are only accurate for this metric when you are at complete rest, such as during sleep.
When pairing a chest strap, your watch will automatically disable the optical wrist monitor to ensure the data source provides the necessary accuracy for functionality. -
When pairing a chest strap, your watch will automatically disable the optical wrist monitor to ensure the data source provides the necessary accuracy for functionality.
It will disable the optical sensor of the watch, but not for the reasons you stated. Suunto just can’t work with multiple sources. On the plus side the disabled sensor will save you a bit of battery…
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Ça va faire un an que j’ai ce problème là.
Ça a commencé avec ma ceinture Polar H9.
Suite à ça j’ai pris une ceinture Suunto neuve et même problème. Je suis très déçu que Suunto n’est jamais résolu le problème …
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