Hi All,

I've had a Garmin Edge 500 for almost a year now. Other than an occasional erroneous reading, or unexpected shut down, it has been very reliable . . . until now.

Friday morning I was playing around with my cleat position so I put the bike on the fluid trainer. For some reason it would not display the speed. It displayed the cadence just fine (through the GSC 10). Since I was going out of town that afternoon, I didn't have a chance to play around with it until today. I tried re-pairing the GSC 10 with the Edge 500, no change (i.e., cadence works, speed doesn't). I tried pushing the re-set button on the GSC 10 - I get the red light flash, the green light flash after pushing the re-set, and a red light when the crank arm/cadence sensor passes by, but no green light when the magnet on the wheel passes by.

I tried it on my other bike (with a different GSC 10 unit) and both cadence and speed seem to work fine (at least on the repair stand).

Any suggestions of what else to try? Is it time for a new GSC 10? Should I replace the battery? I'm open to ideas.

Thanks,

KB

Is the magnet still on the wheel?

Is the wheel magnet lined up with the mark on the GSC 10 sensor when it passes? I have had the magnet get loose and slip further out on the spoke and stop sensing. Also, check the distance from the sensor to the magnet - the sensor arm might have gotten bumped when you put the bike on the trainer.

Yup. The magnet is on the wheel. I've tried repositioning it, i.e., rotating it, sliding it up and down, even adjusting the sensor arm. No luck.

Do you have a power meter? Sometimes your pm can effect the speed reading on your garmin. I had to take my magnet off when I had that problem

Nope. No power meter.

Heard back from Garmin. They suggested repositioning the magnet and changing the battery - both of which I've tried. I just sent them a copy of the receipt showing I purchased it less than a year ago. We'll see what happens now.

Are you aware of Garmin's official users forums? Good place to sort out issues or found out about recurring problems. https://forums.garmin.com/forumdisplay.php?219-Edge-500

In my personal experience and in the experience of others I know, Garmin has been very good about warranty support. They have you jump through some hoops trying things to get the problem sorted, and it that fails, they have you send it in and send you a replacement with pretty quick turn around time.

I am aware of the Garmin users forum. I posted a similar inquiry there a day or so after my original post here. Unfortunately nothing was suggested that ended up working.

Still waiting to hear back from Garmin.

I have been having the same problem with my Garmin 500. Cadence works fine but can not get it register speed. Have changed battery repositioned sensor, hit reset, no help.

These sensors use reed switches to sense the magnets, and these switches can fail or become faulty. The rear wheel averages 2-4 rpm faster than the crank and keeps turning when you're coasting so the wheel sensor sees many times the number of actuations that the cadence sensor sees, which is why it more often fails.

Just to update. Garmin sent me a new GSC10 . Since in the meantime I had gotten used to riding without speed, I just set it aside (while awaiting delivery of my new bike). When my new bike arrived (beginning of May), I put the new GSC10 on it, and everything was working fine - until last week. It still registers the cadence, speed and distance, except that the speed and distance are off, by a significant amount. All of a sudden, it showed my commute to work as 10.5 miles, whereas it's been showing up as 14.3 miles for over a year (since I started commuting). My speed doesn't seem to exceed 12 or 13 mph, even though the elapsed time and known distance result in an overall average of a little over 16 mph. I haven't had a chance to play around with it, re-pair it, or even post a similar question on the Garmin forum. Hopefully I'll get a chance this weekend. Anyone else have similar problems? Suggestions?

Honestly, I'm about done with this Garmin. When it works it's great, but it seems very unreliable. Lately almost every ride has at least one or two spikes where it says I exceeded 99 mph (I'm not that fast, the tailwinds aren't that strong, and the downhills aren't that steep).

Something certianly isn't right. I have two Garmins and 3 GSC10s with a total of over 20k miles between them with no such issues. Only thing I can suggest is checking the distance and alignment of the magnet.

I've had other issues, just not those issues.

I thought the GPS overrode the GSC-10 to measure speed, unless the signal was lost. Are you sure the GPS is on?

Edit to add: the arm postion of my GSC-10 in relation to the wheel magnet is MUCH more sensitive to pickup than the crank sensor. I hhve to adjust the arm so it is almost ****ting the spoke magnet.

The 500 will calibrate the wheel using the GPS. If the GPS is ON, it may show zero on a trainer. Turn GPS OFF when using trainer.

No problems at all with my unit.

It's the other way around. The GSC10 is primary for speed and distance and the 500 reverts to GPS if the speed sensor signal is lost.

Ding! Ding! Ding! We have a winner!

I readjusted the arm of the GSC-10 to less than 5 mm from the magnet, and all is copacetic.

Thanks for all the help and suggestions.