Originally Posted by
eja_ bottecchia
As others have pointed out, a set of precision screwdrivers is essential for the job. Also good eyesight and steady hands (these screws are sure tiny, try not to lose them).
When you replace the battery first install it upside down and hold it in place for 10 - 15 seconds. After that reinstall the battery correctly and re-attach the cover. I am not sure why this works, but the procedure was listed on the Garmin Forums and it worked for me.
I bought this set of screwdrivers from Amazon and they work fine.
I no longer have a Garmin HRM, but this ^^^ was what I suspected the problem was - JIS (Japanese Industrial Standard) screws/screwdrivers look very much like Philips, but they're not the same. A Philips driver will often pop out of JIS screws, which are more common than you'd think. I actually need to pick up a set of JIS screwdrivers to do a little camera lens surgery.