Conflict with electronics!
I have a Vetta V100HR computer (includes cadence and heartrate - only the heartrate part is wireless).
For a long time, I wasn't using the heartrate part, though periodically the computer would show HR numbers - which I chalked up to periodic interference from electrical sources on my route. Usually these numbers were pretty low (like 40).
Then, at some point, I started getting really high numbers most of the time, usually over 200. Then when I decided to use strap on the HR monitor, the numbers almost never made sense - again, being often over 200 (that's way past my max!). I tried replacing the batteries in the strap but it didn't help. So I stopped using it (I had replaced the battery in the computer not all that long ago).
But a couple weeks ago I had a bike tuneup and when I got it back, the HR stayed at zero almost all the time, as it should. I couldn't figure out any reason for that correction, but eventually I put the HR strap on again. Seemed to work while sitting in my apartment, but when I attached the computer to the bike again and started riding, it just stayed at zero!
Well, today I tried again. I started to wonder if maybe my headlight was causing a problem with blocking the signal (a Viewpoint Gen3 Digital model which does sit right next to it and slightly above). So I slid the light off the mount and, sure enough, the HR worked again. So I held the light near the mount, but a little off to the side so it wouldn't physically block a signal. But the HR went back to zero anyway. Eventually I tried turning off the light, but holding it in the same position and the HR worked again. Even when the light was on the mount it worked, but as soon as I turned on the light, it would go to zero!
Now, while I say it worked with the light off, I should point out that there was some inconsistency - it would work and then not work for awhile, back and forth. Also, the numbers often didn't make sense, almost as if it was only picking up half the heatbeats or 2 out of 3, etc. Basically it seemed that even having the light near the computer unit MIGHT affect it, but not always. Turning the light on always killed it.
Riding home, I put the light in my backpack, but the results were still intermittent, which baffled me.
Then I remembered that there was a period of time when the computer usually didn't do the automatic shutoff (where it only shows the time). So I thought maybe that was because of the light causing interference even when off and so perhaps part of the problem was that the battery had drained much faster than normal, even though speed, etc, all seemed to be fine. I replaced the computer battery and the HR started working well IF the light was not near it. If the light was there, it might give results that were too high. If the light was on, the numbers tended to go even higher, though there was not absolute consistency on that, but almost.
Anybody else ever experience anything like this? Besides using a different light (really can't afford that, especially if another might do the same thing!), anybody have any solution? I've tried moving the computer and light as far apart as possible, but the change was only an inch or so which isn't going to do it. All my rides typically involve riding 36 miles or more while it is still dark, then I do 14 or so in daylight after breakfast.