My b16 civic runs weird when its cold out.. when its real cold and the engine is warmed up the temp gauge is at normal opperating temp.. but if im driving down the road and turn the heat on the temp gauge goes down..the heat is not real hot buts it pretty warm i guess.. could it be the thermostat? if it was the thermostat wouldnt it do the same thing even when i didnt have the heat on? i need some suggestions before i go taking **** apart.

 

I have something like the same problem... I think it's a grounding issue, because it's not consistent. Doesn't do it all the time.

CHeck if your radiator fan comes on. If not, it's a thermostat problem...not a gauge problem.

 

i am having same problem bump to find an answer

 

thermostat guys, when you turn on the heater, you are further cooling the coolant with air blowing through the heater core (2nd radiator). My accord does the same thing, I am 99 percent sure the t-stat is staying open. the whole time.

 

Well just an update for you guys... I fixed my overcooling problem, it was after all a grounding issue, I redid my battery ground and that seemed to fix the problem. I already bought a new t-stat earlier so i replaced that anyway, No Problems now, thanks for the help