Suunto smart heart rate strap freezing after ~30 minutes (Tried battery replacements & cleaning)

[sszabo.apor]

Hi everyone,

I’m reaching out to see if anyone has experienced a similar issue or has any advice.

I’ve had my Suunto heart rate strap for about 3 months now, and it has been working great until this past week, when it started acting really strangely.

The issue:
Every time I go out for a session, everything works perfectly for the first 30 minutes. After that, the heart rate data suddenly freezes/gets stuck on a single value and doesn’t change at all for the rest of the workout, no matter my effort level.

What I’ve tried so far:

Replaced the battery 3 times already to rule out a dying power source.

Next on my list is to thoroughly clean the snap connectors and contacts using a soft toothbrush.

Has anyone run into this exact “freezes after 30 minutes” behavior? Could it be a hardware failure, an electrode/strap degradation issue, or something else entirely?

I’ve attached some photos of the strap itself and screenshots of the data flatlining/freezing during a workout below.

Any tips or troubleshooting steps would be greatly appreciated!

Thanks,!

[elbee]

@Apor-Szabó

Could be the quite common problem where the watch looses connection with a bluetooth device and fails te reconnect.

There is no solution for that problem. Suunto should solve it but I don’t have the impression they are very active looking into it.

[sszabo.apor]

@elbee Thanks for the insight! That definitely sounds plausible. I’m still going to keep tinkering with it and hoping it cooperates properly at some point, but it’s good to know I’m not the only one running into quirks with it.

[Maximfreediver]

@Apor-Szabó
Exactly the same problem, they change it for new one and i’ve got same problem with new. Now i don’t know what to do, because two belts, even new one has the same problem. My watch is Suunto Ocean. Did you find any solutions?

[elbee]

@Maximfreediver

There is no solution. There is a major bug in Suunto’s bluetooth firmware. Suunto either cannot fix it or aren’t looking. (And in my case, I think it is highly unlikely if suunto has a fix it will ever be available for my race s)

I do notice that regularly reboots (like weekly or more frequent) help to mitigate the problem.

[Petr Dubský]

On Thursday, I recorded an ice hockey session using a new Suunto strap, following the instructions exactly; I left my Race S watch in the locker room, and after the session, I stopped the activity and waited for the data to sync to the watch. Upon checking, I found that the heart rate graph only starts at around the 50-second mark of the activity. This also happened during my previous session when recording to the Suunto Smart HR memory. Am I doing something wrong? Thank you.

[Squirrel]

@Petr-Dubský said:

I found that the heart rate graph only starts at around the 50-second mark of the activity

You mean 50 minute mark
Do you have new HRM2, or previous Suunto HRM?

[Petr Dubský]

@Squirrel Máš pravdu , zaznam TF zhruba po 50 minutách , napsal jsem to špatňe , mám suunto smart sensor zakoupen 7/2026 chtěl jsem zaznamenávat aktivitu (TF) bez hodinek a stále mám problémy, jaký je správný postup synchronizace HR SUUNTO SMART po aktivitě .
Děkuji

[sszabo.apor]

The fix ended up being simple: I just bought a new sensor from Decathlon XD, and everything works perfectly now. If they push a fix or update things in the near future, I might switch back to the original sensor and strap.

[CroShark]

@Petr-Dubský I have the same problem with my Vertical 1 and Suunto Smart sensor.
Every thing was working fine until one of the firmware updated. Now almost every cage football the same. Incomplete hearth rate data.
I tried creating a topic about it, but got no responses on the forum.

Like you said, start the activity in the locker room, leave the watch. After the match stop the activity, the watch syncs the HR data. Still after that a large part od data is missing.
This is the main benefit of using the Suunto sensor, and it works maybe half of the time.

[elbee]

@CroShark

Report your problem to suunto support@suunto.com

Have to say, I have reported it multiple times (my race s looses it’s connection to my polar oh1+ and stryd quite regularly), but I don’t think suunto is actually working to fix the problem. They told me not to expect a firmware with a fix anytime soon (and I think anytime, for my race s)

Do have to say, regularly reboots (as in every week) does mitigate the problem.