My heart rate strap has stopped working so I'd like to change the battery. The four screws on the back are tiny and even the smallest precision screwdriver I have is too large. Does anyone know what size screwdriver is required?
Note: if it doesn't work with the new battery, you may find you just need to short the terminals with a piece of wire or a coin (it releases some built up static or something). Some Garmin HRM straps (including mine) need this "fix" applied every year or two.
No need for shorting terminals, the garmin instructions recommend leaving it for 30 seconds without a battery, problem solved and procedure carried out as the designer intended.
Another good way to short the terminals is to put the battery in back to front, I generally do it when ever I fit a new battery to a Garmin HR strap (have also used this trick on a few straps and sensors from other brands)