Rep Power: 0

In the winter my temperature gauge pegged a few times. It went away for a while and now it pegs as soon as the car turns on. I replaced the temperature sending unit. The problem persists. I'm fairly certain that I've seen the cooling fan on once while this problem was going on. Any other ideas guys?

 
Rep Power: 245

Thermostat possibly. Is the engine actually getting that hot?

 
Rep Power: 812

if it pegs as soon as car starts, its a bad engine coolant temp sensor (ECT) right above the thermostat housing.

 
Rep Power: 0

I already replaced the thermostat when the problem was intermittent. Now that it happens as soon as I start the car - I doubt anything could get that hot that fast.

Gearbox, I'll take your advice and replace that part.

...just so we're clear. the part is right next to the sending unit, which I just replaced. Correct?

 
Rep Power: 812

yup ECT sensor is the one you need to replace with a new o-ring. it tells the ecu when the engine is warmed up and it has a gradual thermistor. if it fails, it could read always hot or always cold.

 
Rep Power: 0

So I replaced the ECT sensor and the gauge still pegs. Is there a fast/easy way to test the gauge and the wiring to it from the sending unit? What's the difficulty of replacing the gauge if necessary?

 
Rep Power: 812

you would need to replace the entire cluster, they are cheap on ebay but you need to find the right one and also one with similar mileage. you could open yours up tho and see if the temp needle feels normal. maybe it just got off its track.

 
Rep Power: 0

So I replaced the temperature sending unit - the problem persisted. After giving up and letting several weeks pass, I accidentally discovered that dimming the dash lights temporarily brings the temperature gauge down to where it actually should be. After a moment or two, the gauge climbs back up, along with the dash lights coming back to full brightness. Any ideas on how to rectify this? Any of you ever seen that before? Thanks for all the help!

 
Rep Power: 0

hello I have the same problem you solved it somehow thanks and greetings