Hey so my 1999 Civic lx just started having this issue since I let it sit for a couple of days. The temp gauge works as it should when the key is at the ON position but when I start the car, its just starts moving up and down like crazy. The car is not actually over heating because i have fixed the issues it has had in the past and the temp gauge reads correctly when its just on the ON position. Ive checked the grounds but all seem to be connected and clean. Any suggestions?