# Edge 500 - Strange Problem - Help!



## Major Clanger (Feb 11, 2012)

My Garmin Edge 500 (with speed/cadence sensor) has developed an odd problem that's occured twice in bad weather...

The unit starts to cycle between aucto stop and auto resume even though I haven't stopped moving. More seriously the speedo is very erratic and the odometer over-reads to a large degree. As an example, I did a measured 50 mile charity ride yesterday and the odometer reads 76 mls. Strangely though, I checked the speed against other cyclists yesterday and the Edge appeared correct and so I'm very confused.

Here's a link to the ride yesterday where you can see how erratic the speedo is, and also the odometer. I've checked the rolling circumference setting and everything appears okay.
by at Garmin Connect - Details

The unit's under guarantee so shall I just send it back or is there something I should check first. The problem only occurs in poor weather, normally it's fine. Yesterday was just light showers though, nothing dramatic and I can believe the unit isn't weather resistant at all.

Over to the GPS wizards and thanks for any input......


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## ghettocruiser (Jun 21, 2008)

connect.garmin.com said:


> You do not have sufficient privileges to view the activity with id 175505020.


.....


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## Major Clanger (Feb 11, 2012)

Sorry, privacy settings, try this instead.... by at Garmin Connect - Details

You'll see that my speed reached 130mph several times which is a good effort! Oddly though, the cadence looks about right so I don't think it's the sender unit. To compund matters, I took the head unit out earlier in the car and drove 10mls and the unit measured pretty much the same, so it does seem weather related.


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## ghettocruiser (Jun 21, 2008)

Still getting denied, even signed into my own GC account. Can anyone else see it?


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## Harold (Dec 23, 2003)

nope


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## Major Clanger (Feb 11, 2012)

Okay, I'm going to PM you both........


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## Harold (Dec 23, 2003)

this one?

http://connect.garmin.com:80/activity/embed/175505020


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## Major Clanger (Feb 11, 2012)

Yes, that's the one.


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## Harold (Dec 23, 2003)

when was the last time you changed the battery in your speed/cad sensor? what about the sensor arms relative to the magnets?

your speed has the most wonky spikes, but there are a couple in your cadence graph, also, and the time stamps closely correspond to spikes in the speed graph.

I would map out a route, say, 5mi or something like that around home. go out and ride it with the GPS using the same settings as your charity ride. Then, disable the speed/cad sensor and do it again. I'm hedging my bets that it has something to do with that sensor, since your GPS position seems to be fine.

Now, whether the sensor arms got bumped and they're too far from the magnets, whether the battery is low, or whether the sensor itself is on the fritz, I can't say. but I'd say it definitely warrants further testing and investigation.


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## ghettocruiser (Jun 21, 2008)

Word. When I download the GPX and re-upload it, it wipes out the spikes. (which is a method you can use to correct your own data) 

So the GPS data is fine. I concur your speed/cadence sensor must be acting up.


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## Major Clanger (Feb 11, 2012)

Thanks both.....

The magnets for speed/cadence pass within 3mm of the sender unit so that seems fine. I haven't checked the battery but the whole package is only 5 weeks old so would be surprised if it was that (although I have another bike with a sender unit that I can test against it).

It seems odd that the problem only manifests itself in wet weather. There's a lot more to the programme software on the Garmin website by the sounds of it - I shall have to learn to use it properly.

Thanks again and I'll let you know how I get on. Now, screw those username/passwords into small balls and swallow them......!!


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## Harold (Dec 23, 2003)

Major Clanger said:


> Now, screw those username/passwords into small balls and swallow them......!!


you'd be wise to just change your pw at this point. wouldn't want one of us to wipe your whole ride history, or figure out where your house is and empty the place. :thumbsup: 'cause really, who can you trust on the interwebs? 

as to the weather question, how many times has this occurred? I don't think I'd rule out the possibility of it being weather related. however, unless this has happened more than a dozen times, and only in the rain, I'd also be open to the possibility of weather only having a coincidental association. you could test that idea by spraying the sensor with a spray bottle every mile or so on a couple test rides.


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## ghettocruiser (Jun 21, 2008)

Major Clanger said:


> TNow, screw those username/passwords into small balls and swallow them......!!


So wait, you *don't* want me to upload a bunch of tracks from the Garmin-Cervelo team to make it look like you rode the Giro D'Italia?


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## Major Clanger (Feb 11, 2012)

ghettocruiser said:


> So wait, you *don't* want me to upload a bunch of tracks from the Garmin-Cervelo team to make it look like you rode the Giro D'Italia?


Wow, you can do that? In that case let me give you the access codes to my bank account and you can work some magic there as well..... :thumbsup:

Thanks again both, I'll report back once I've tested the sender unit.


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## shiggy (Dec 19, 1998)

Major Clanger said:


> Thanks both.....
> 
> The magnets for speed/cadence pass within 3mm of the sender unit so that seems fine. I haven't checked the battery but the whole package is only 5 weeks old so would be surprised if it was that (although I have another bike with a sender unit that I can test against it).
> 
> ...


Might be the unit leaks and the battery/electronic contacts go wonky in the wet.


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## nov0798 (Nov 27, 2005)

Did you manually set your tire circumference? I had a similar problem on my mountain bike. I solved the problem by using some epoxy and adding a stonger magnet from ACE hardware. Like these, just the smaller one.

Master Magnetics® Super Magnet - Magnets & Pick Up Tools - Ace Hardware


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## Major Clanger (Feb 11, 2012)

Thanks all for the input. It's the sensor unit itself which is fried..... I've swapped the head unit back and forth between bikes and ridden the same route and have established the problem.

I shall miss speed readings of 90mph on my cycle to work though.......................


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