My Garmin heartrate monitor stopped recording the other day. “Easy enough fix,” I thought. “I’ll just replace the battery.”

I walked to the grocery store down the street and picked up a brand new CR2032 button cell battery for it. I replaced the battery the same way I’ve been replacing batteries my whole life, screwing the backing on as the last step. Then I snapped it back on the strap to make sure it pairs correctly with my Edge 500 computer. Nothing. The computer doesn’t find it.

I searched Garmin’s website to make sure I wasn’t missing some sort of secret step in replacing a battery and found a link to this article. It basically says to make sure to drain the residual charge from the monitor after removing the old battery and before putting the new one in. I guess that could make sense: something you do when working on a desktop computer is hit the power button one more time after you turn off the power supply to flush the residual charge.

So I followed that page’s instructions and it found the monitor.

Only for a few seconds.

Then nothing.

Weird.

I’ve purchased a handful of Garmin devices over the past few years and each of them came with a new heartrate monitor (and I’ve burned through all of their batteries). But one thing I’ve always done is left the straps themselves unused while re-using the old one I’ve been using for a few years now. I dug into a box to find an unused strap, snapped the monitor into it, and the computer paired with it almost immediately.

It turns out it was the strap that had failed. Just another thing to keep in mind while doing maintenance.

Note to self: buy a multimeter.