Faulty Temperature Gauge
courtesy of Bob, The Auto Answer Man
I have a 6 year old Ford Contour that has 55,000 miles. The last two years my temperature gauge has been acting funny. This happens mostly during the summer when I run the A/C. The gauge will come up to temperature and then "bounce" back to below the "C." Sometimes, it won't even move off "C," and then all of a sudden, it will move up to normal (even though the car has been running for a long time). I have tested the thermostat and a control that sits on top of the thermostat housing. Both checked out fine. I'm guessing that it is just an electrical problem because the car runs fine and I don't overheat. What do you think the problem could be? I have a Haynes repair manual and I would try the repair myself if it's not too difficult.
It sounds like it could be one of a few problems. Some of which you seemed to already have ruled out, but I will enumerate anyway for the rest of the readership.
Air pocket. There could be an air pocket or bubble that is floating around in the cooling system fooling your temperature gauge. However, more likely than not, you will soon overheat. This does not seem to be the case in your situation.
Faulty temperature sensor. This is most likely your problem. There are several temperature sensors located on your engine. Each one, sends a signal to a different circuit for different analysis. Generally, the one that signals the gauge is the least secure and most likely to fail since it is not a critical system. Another possibility could be a loose wire going to the sensor. Try the wiggle test and see what happens.
- The gauge in the dashboard could be faulty. Generally, this does not happen, but as with everything else, it is a possibility.
Attempt to locate the sensor that signals the dashboard gauge. Before removing it from the engine, disconnect the wiring harness from it to ensure that it is the correct one. Bring it with you to the auto parts store. I can almost guarantee that if you don't, you will get the wrong one.
Bob, The Auto Answer Man
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