Argh! Hyper-annoying computer problem
 

I'm using a Cateye Enduro 8 computer (yes, it's an MTB one ...) and the last couple of rides it's developed a habit of "cutting out" from time to time. But here's the infurating part, especially since I like to monitor my average speed. It only happens on downhills! I'm sure the problem's at the computer end rather than the sensor, because if I handle the computer (or sometimes hit it, sometimes VERY hard) it starts working again. If I don't touch it, then sometimes it starts by itself in the end, but otherwise it will just read zero, or very low mph figures, occasionally it will read about half my actual speed for a while.

Anyone want to hazard a guess why this is happening? I've checked that it's seated in the mount correctly. The computer is only about nine months old so it shouldn't be the battery (and why would a low battery cause that problem anyway?).

Thanks in advance for any opinions

Are the magnet and the sensor lining up? Are the contact points clean?

Check the alignment of your wheel sensor against the pickup. If they're not lined up well you may get intermittent readings. Also try cleaning the contacts on the computer body and the mount with a pencil eraser. If the fit is loose, you could try adding a shim (maybe some folded paper) to hold the computer more tightly in the mount. Worst case is that you might have a wire coming loose either from the pickup or the mount. If that's the case then you either need to break out your soldering iron (you do have one, right?), or get in touch with Cateye.

Yes, and as far as I can tell (though I'll clean them again before the next ride). But why would it only happen downhill?

I have glue, tape and elastic bands. ;)

The fit in the mount is tight. Could be a loose wire, but could it also be losing contact because the contacts aren't pressed closely enough together? In this case, is there anything I can do?

is it cordless?

Sounds like it's a battery issue or the magnet is going too fast for the detector to record speed. Try placing the magnet/detector closer to the hub.

Thanks, but I don't think it can be the sensor, as I can always fix the problem by wiggling the computer. Also, it's only just started playing up and the sensor's been in the same place for ages. The instructions say the battery should last 3 years at an hour a day. That's about 8 times as much use as I've had out of it. But I'll replace it and see what happens.

BTW, it's not cordless - in fact it's got a thick wire which is meant to stand up to mtb-style abuse.