So over the winter my Garmin HR strap started acting up. At first I thought that it was the cold. Once I got a good sweat going to get some good contact between my body and the strap it would be fine. In January I tried a new battery, and there was no improvement. As the winter progressed I would get an increasing amount of bad readings from wind hitting my chest as well, and now that it is warm and there are no layers keeping the wind from buffeting the thing (or from stopping the buffeting of other clothing into it) the strap is almost useless. Prior to the start of last winter, the only time that I got erroneous readings from the strap was during a short stretch while descending Mount Ventoux in some crazy wind, to give you an idea of what it has taken to make it give bad readings in the past.
It has spent a large part of the last month of rides pegged at over 200 bpm, when a reading shows up at all. At this point I know what my heart rate is at what effort, and I can tell that when I do get readings they are flaky. It does work best when I am going up a significant hill as I guess I am breathing hard, there isn't much wind, and there's a lot of sweating going on.
The GPS in question is a Garmin 305 that I purchased late in December of 2008. The only question I have is if anyone has had luck getting a new strap from Garmin? I've done nothing to abuse this thing and it has crapped out. It's got basically no wear on it.
It definitely sounds like a conduction issue - have you tried washing the strap itself real good? They tend to get really dirty obviously from the sweat. The build up, especially around contact points could prevent it from conducting properly. This is common for new transmitters with soft straps that house electrodes(I work @ Polar) A good wash may solve the problem =)
You are experiencing what many of us call FJS (flapping jersey syndrome). For some reason the Garmin HR starps suffer from static electricity build up. It is the worst in cool dry climates. In addition some of the synthetic fabrics in base layers and jerseys make the problem worse. I have not found that gels helped me much. Once I get warmed up on my rides the problem goes away. It normally only returns on descents when the jersey is flapping.
I ordered the heart rate monitor from Amazon, and was pretty happy with it. Except, after two weeks, I started either not having a heart rate, or working so hard that it would be about 240 bpm. And always the same number, whatever it was, in that range, or no reading at all. I tried replacing the battery, but to no avail. Oddly, though, the battery compartment had some kind of awful goo. I sent it back to Amazon, and the new one hasn't given me trouble since. It sounds like we were having the same problem, though.
I hadn't noticed any impact from the wind, but I've usually had a jacket on. And I use a merino ( wool ) base layer, which seems to keep static out of my way.
A merino base layer. Why had I not thought of that? I've pretty much quit using my wool jerseys as they are just too saggy, but I had not thought of using a merino wool base layer rather than the smelly synthetic I've been wearing. This has nothing to do with the heart rate sensor but thanks for mentioning it (well, maybe it will help that situation as well). I'm about to load up on some wool-y goodness.
I love my merino. For me it's more about the wicking of sweat ( you know that feeling when you finish climbing a hill, and suddenly you're hot from the work but cold from sweating in the breeze? ) and being able to end a long ride without stinking.
Anyway, I hope this isn't obnoxious, but if you check out a pair of brands called stoic and backcountry (dot com), they have a few really soft merino tops at about half the price the local bike shop or REI charge. And they're softer than cotton, especially the 17.5 micron stoic ones. I don't work for them or own stock or anything, but good wool is expensive, and it's nice when you find a deal. I've heard good things about minus33, too, but haven't tried them personally.