I’ve had various Garmin cycling GPS devices for almost nine years. I’m a fan, as you will gather from my posts about the Edge 800 and Edge 1000. I’m now mainly using an Edge 1030.

In the past few weeks, I’ve found that the heart rate reading showing on the Edge was wildly inaccurate early in a ride. In some cases, by 60 beats a minute compared with the rate on my Apple Watch. Often the Garmin rate would be falling, even though I was climbing a hill. What was going on?

I followed the care instructions, wetting the heart rate strap before every ride and washing it regularly. But to no effect.

Finally, the penny dropped. I wasn’t wetting two small rectangular patches on the band. here’s one on the right of the band:

And here’s the other, on the left of this photo (in the middle of the band):

This should have been obvious looking at the diagram on the band:

Once I wetted all four patches, the Edge tracked my heart rate perfectly for every ride. That saved me buying a new strap!