I've looked to see if there was a replacement for the temp gauge sensor. Didn't find any info on one that would work that could be bought locally. Has anyone tried to clean said sensor and did it do ant good. My temp gauge started acting strange. In this heat{100*+) it will move off the white square dot just a tiny bit. For a couple of days the gauge would stay just above the white square then jump to the middle for a few seconds then drop back down.The bike is not overheating and the fan comes on when it should. Only the gauge is not reading right. Took a ride a little while ago and the temp was 106 by the NWS and my temp gauge read 117 but the bike didn't get hot (didn't over heat)
I've never heard of one going bad on a C-10. The manual suggests testing it by crossing the leads briefly, it should simply peg. Then you break contact or the needle might break.
Maybe yours is as simple as a dirty connection somewhere? That's the only reason why I can think it would work intermittently....
The “Plug sensor water” (Dang engineers.lol) Is a single wire device located on back side of thermostat. The lug that connects it often come's loose some try to spread the rivit with punch and hammer, But I filled mine in with a iron and solder. That's where I would look first and Good luck.