My temp light is flickering

[sickfleming]

Ok. This is for my 1994 Buick Century 3.1 145k miles. After looking through the forums, it seems that I can't find any info on this. My temp light is coming on. It flickers on and off very rapidly as I drive. The gauge itself is fine, although when idling the other morning it shot all the way till the red zone, plus the heater wouldn't work. I shut the car off immediately and turned it back on moving the heat on and off switch from side to side, then the heater finally came on and the gauge quickly returned to normal, between the quarter and halfway mark. I popped the hood and felt the engine. It wasn't very hot. I'd only been driving it for around 20 minutes. Anyway, I replaced the thermostat, coolant temperature sensor (not the pigtail) and gave the system a flush and added new coolant. It still comes on. I do NOT use dexcool. That was for '95 or '96 onward. The original owner kept putting water in the system so do you think it could be corrosion? Or is it transmission related? Other than that, the car doesn't do anything out of the ordinary. Thanks!

 

[MelsRegal]

did you bleed the air out of the system when you changed the thermostat? have you pressure tested the cooling system? have you checked for hydrocarbons in the coolant?

 

[sickfleming]

The air was purged after I flushed the coolant. I haven't pressure tested it. Hydrocarbons? You mean corrosion? I thought I flushed it out. Again, it doesn't run hot and the gauge is accurate. It's just that light.

 

[MelsRegal]

the hydrocarbon test checks for the presence of exhaust gas in the coolant indicating a blown head gasket or something related. If the only concern at the moment is the flickering light the easiest thing to do is change the sender

 

[sickfleming]

Ok. Like I said, the sensor has already been replaced. However, yesterday the temp gauge itself kept flying all over the place. One second cold, next second it's off the charts, then back to cold, then back to normal after a few minutes. So I'm pretty much assuming that the engine is running ok. I might have a short somewhere or something, I think.