Why Isn’t My Heart Rate Monitor Working? Because It’s Dirty
Why isn’t my heart rate monitor working today?
May 2020 UPDATE: You can go thru the process of cleaning your heart rate monitor regularly . . . but seriously, just get a Polar H10. You’ll see in the comments below that I switched from saying, “A lot of people in my forums recommend it” to “I got one, and I recommend it.” I got mine Dec 2019 and it’s been just about flawless. The first battery ran out quicker than I expected . . . in March. The replacement is still going. No connection problems. No data drops. No data spikes. Will report again in December. Again, skip the frustration … just get the H10.
That’s a question I never want to ask myself yet I have several times this year. I have two Suunto watches — for tracking my triathlon training, mountain adventures, and navigating in the backwoods — the Spartan Ultra and the Spartan Sport Wrist HR.
My Heart Rate Monitor: Suunto Smart Sensor
The Suunto Spartan Ultra (SSU) doesn’t have HRM on the wrist, so I always wear a chest strap with it.
While the SSSWHR model has an optical heart rate monitor on the wrist, I wear a chest strap heart rate monitor all the time with that one too since chest straps are slightly more accurate … by all the time I mean except swimming, since pushing off the wall nearly always has enough force to slip the chest strap out of position and that’s mad annoying.
Anyway, things were going swimmingly … two watches, one heart rate monitor strap synced to both, connected quickly and flawlessly every time … for 7 months until one day in July things between my SSU and my HRM went south.
Heart Rate Monitor Frustrations
At first how it went is I’d go to the “pre-start” screen where the watch is locking in connections just before starting an activity, and the screen would show a connection to the Suunto Smart Sensor HRM (which connects to the watch via Bluetooth), even indicating my present heart rate. But as soon as I started the activity, the watch showed my heart rate as “—-“, and when I later finished the activity synced the data to Movescount, there was no heart rate data. Annoying.
So I tried stuff like unpairing my watch and the heart rate monitor. And repairing. And the same thing would happen.
And then it got worse … my SSU just stopped finding my HRM at all whenever I tried to re-pair.
I replaced the battery, hard reset the watch, un-paired the HRM from every other device and on and on … all to no avail. But there’s a good ending to this story.
In case you’re wondering, yes, I was soaking my chest strap as well to ensure there was enough moisture to conduct electrical pulses from my skin and so the chest strap had something to read and data to relay through the device.
Almost the whole time through this, I could still get my SSSWHR to connect … almost.
For awhile, my heart rate monitor performance was unpredictable, and I couldn’t stand it.
I mean really couldn’t stand it.
I count on heart rate data in my workouts to track how much work I’m doing and how much at what intensities. Without the HR data, my data has gaps and I my aggregate numbers get off. Since I really want that data, and I couldn’t get it from my SSU, it became almost unusable for me for awhile even though it is an amazing watch and can do so many other things.
This was no good.
It’s supposed to be a great watch! It IS a great watch! I’m the U.S. Endurance Community Manager for Suunto!!! … but my watch, within year 1, isn’t working!!!
Not a good situation.
Trawling the Internet for a Heart Rate Monitor Solution
Through my various attempts to getting a connection to happen, I did clean my strap. But not really clean it.
In trawling the internet for what people do about their HRMs, I found a forum post where someone went into depth about cleaning it. I decided to go Type A and clean every single thing I could to see if that would work. Because if a deep clean didn’t work, then it truly was a product defect and I’d send it back for a replacement.
How I Cleaned My Heart Rate Monitor
Prep: disconnect, un-pair, “forget” or otherwise completely sever the connections between your HRM and your watch, phone, bike computer and any other device you’ve connected it to. Get a bowl, dish soap, rubbing (isopropyl) alcohol and cotton swabs / q-tips.
Step 1: Fill a bowl with warm water and some dish soap. Place the chest strap into the bowl. Let it sit overnight.
 Liquid dish detergent and laundry detergent are best.
 By “warm” I mean less than 100F (<40C). So, like “the middle” of your hot and cold settings. Very lukewarm or maybe a tad on the “when I put my finger in to test it, it feels slightly chill.”
 Yes, a bowl and not the laundry even though that’s what’s in the user guide.
Why? According to my biochemist bro:
For dish and laundry detergent: they don’t have any moisturizing additives that leave non-conductive deposits behind. The whole point of washing is to get rid of the non-conducting oils.
For water temp: hotter water will do a better job cleaning, BUT above 40C it will damage the elastics & stretchy fabrics in the band. And that breakdown is no good. (Fwiw, 40C is the hottest recommended temp by Suunto in the user guide.)
The crud that builds up on the electrodes and makes them non-conductive (so you stop getting accurate readings consistently) is a mix of greasy skin materials. Sweat is bad for your HRM band and the electronics because sweat includes oils and salts. That combination loves to stick to smooth, rubbery surfaces like the electrode pads. Detergents are their enemy and will wash them away.
And my take on why soak overnight instead of tossing in the laundry machine per the user guide (English PDF, other languages): less wear and tear. I’d rather my band sit in a little bit of water than get tossed around with my jeans.
H/T to Dimitrios Kanellopoulos for starting a convo with me that lead to adding this info! He’s active in this Suunto users group on FB. Join us.
Step 2: While the chest strap soaks, open the HRM to replace the battery. And then clean the battery with a q-tip and rubbing alcohol, on both sides. When the alcohol has evaporated, put the battery in. Using the q-tip and rubbing alcohol, swab around the sealing edges of the case but don’t swab directly on the electronics board. If the battery connectors look dirty, carefully swab those. Swab the entire removable casing/shell/battery cover. Finally, reinstall the cover.
Somewhat risky step … not liable for anything that may or may not happen if you do this: if you are still having data consistency issues after all this, some people say to put the battery in upside down for about 20 seconds. Not recommended because reverse voltage can damage electronics, and while the sensor probably has some voltage regulating safety bits, it’s best not to stress them with a battery the wrong way.
Step 3: Clean the connector terminals on the sensor. Whatever brand of HRM you use, there are likely two metal posts on the sensor that “snap” into the chest strap. That’s what I’m talking about. Swab those super clean with a q-tip and rubbing alcohol as well.
NOTE: Rubbing alcohol will also damage the elastics. So be careful where you swab (same in Step 5).
Step 4: (Next morning) Remove chest strap from water and dish soap solution. Rinse out the soap.
Step 5: Again with a q-tip and rubbing alcohol, swab out the receivers on the chest strap where the posts on the sensor snap in. Really get in there to wipe them clean.
Step 6: Let all the alcohol evaporate, run the chest strap under water or apply electrode gel. Put the strap on. Snap your sensor in. Reconnect to your devices, one at a time.
Step 7: As a result of your cleaning efforts, enjoy a HRM that works!
I Cleaned It. That Worked. Heart Rate Monitor Restored.
So after all that my SSU found and successfully paired with my HRM and hasn’t skipped a beat since.
So . . .
Yeah . . .
(Chest strap) Heart rate monitors need clean electrical lines to sense the electrical pulses of our heart beats and clean lines to send all that info from the strap to the sensor. If those lines (in the strap) and connections (from strap to sensor) get too dirty (easy to happen when you train daily and jump in a lake now and then), then they need to get cleaned.
OK! Now I can stop ranting about my HRM not working … because I know it’s my job to clean it.
New ritual: HRM deep clean every 2 months.
Between Deep Cleans, Try This:
Put a small drop of dish soap on the soft side of a kitchen sponge, and then quickly swipe the contact pads. This will keep the contact pads cleaner so you can go longer between deep cleans.
[FOR REFERENCE: I hear people have success using the Polar H10 belt and Bluetooth enabled HRM transmitter, and they say it’s more robust than the Suunto Smart Sensor, requiring less maintenance.]
[UPDATE Sep 2018: I got a Suunto 9 in June when it launched and have sold the Sport WHR.]
[UPDATE Dec 2018: I also sold my Ultra. All-in with the 9.]