After waxing lyrical about how good the 305 is (and has been for a couple of years) now the heart rate readings are all over the place, today running along at tempo pace the readings were down under 100 so clearly wrong. The battery seems to be ok giving out 3 Volts. Any ideas?

As you have been using it for 2 years I presume you have tried putting a little water on the electrodes to get a good connection?  Other than this, not sure.  Have you tried contacting Garmin?

Do you use the chest strap Andy? I tend to replace the coin battery every 12 months as they are so cheap and have never had any prolems.

Hi Guys, yes tried water, yes chest strap, tried changing battery, tried borrowing other runners straps but they don't seem compatible and i get no readings at all. Mailed Garmin but no response. 

Hi Guys,

just an update which may be of use to anyone with similar problems. It was a fault with the strap as when i tried a friends strap (and got the watch to find it..not obvious but on one of the menus) it worked fine. 

Garmin did come back and say i could just buy another strap which are about £40 on the web or £50 from Sweatshop. I ended up biting the bullet and buying a new  110 for £120 which includes a chest strap which i can use with either watch which seemed the best option as i now have a spare GPS watch. and can still use the old 305 which i am used to.

Hi All,

I have a Forerunner 210 that I bought about 18 months ago. For nearly a year the HRM was fine and then it started giving very erratic readings.

6 months ago I replaced the strap with a Polar Wearlink+ as the Garmin transmitter fits it OK. So far it's been good, but I have to admit the Garmin Premium strap was good at that stage too.

The Polar strap was much cheaper too, which was a bonus.