Are you sure it was a "rare earth magnet"? A rare earth (or "neodimium") magnet is VERY VERY strong and should have NO problem disrupting the electromagnetic sensor buried beneath the asphalt. However, you DID say it was capable of holding 100 lbs, which is typical of some larger neodimium magnets. Hmmm... I would say, take it off until you find a light that REALLY does not change for you at all. Then put the magnet back on and go to that light again. You'll definitely notice a difference my friend

 

Oops I hope this doesn't double post. But I recently ran through the msf instructor course and one of my classmates had a name and number to a guy who works for the state of Illinois and adjusts the sensitivity levels of sensors and aparently is very responsive. So I imagine if Illinois has one every state has some sort of rep or office that can do this also. So you could make some phone calls and find out if you have a really troublesome intersection.

 

Here's a snip of what Cycle Gear sells for this...

 

gotcbr, I imagine that device is probably just full of magnets. And for $14.99 you could get a LOT of neodymium magnets. I wouldn't waste my time or money with that thing.

 

Just submitted for information purposes...not a recommendation or endorsement on my part. Some folks would rather just buy a pre-made product than mess around w/ rigging something up.

 

gotcbr, I wasn't trying to come off as shooting you down or anything. I apologize. Haha it's really not required that something needs to be rigged up. Really, all it entails is pulling the magnet out of the package and sticking it to the drain plug or some other steel part on the bottom of the bike.