We have replaced the sensor twice now and it still pegs on high. Sometimes when we just start up the car, other times after we are driving. Have spent $400 now and are very frustrated. Any help appreicated.
Check the wiring.
What type of Subaru, year, mileage? That may or may not help folks to provide more helpful info.
When you say it ‘pegs on high’, do you mean you start it up cold and immediately the gauge goes to high, or does it gradually move to high and then stay there?
It is a 1999 Forrester with around 245, 000 miles on it. It goes to high either immediately or within a few miles.
There are two sensors for monitoring the coolant temperature. I assume you are working on the correct one. The one for the dash gauge should have a single wire tied to it. If you have replaced the correct one already then the wire between the gauge and the sensor most likely has a ground fault on it. You will need to trace the wire and look for a problem on it. If the wire isn’t the trouble then the gauge itself has a problem.