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Q: Temperature gauge goes to high when car is stopped

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Just noticed this today. When I'm driving with my A/C on, my temperature gauge is in the middle. When I'm stopped, the temperature gauge goes steadily up to high and then I'm driving again it goes slowly back down. I thought it was the two fans in front of the engine but when I parked and had the car engine on, I saw the two fans spinning. Not sure what the issue is. I just had the mechanic do some routine things to my car last month and the inspection report showed everything was fine, even the coolant and engine fluids. I have a buyer for my car already, but would like to know what is causing the temp gauge to go up and what fixes/quote would be required.

My car has 122000 miles.
My car has an automatic transmission.

A: To begin, this isn’t something an inspectio...

To begin, this isn’t something an inspection would reveal unless the mechanic was specifically looking for it.

Firstly, how high does the temperature gauge rise when you come to a stop? It is normal for this to occur, especially in warmer climates such as Arizona or Nevada. If it continues to rise into the red, then it is definitely a problem however.

The next possibility has to do with air flow through the fins of the radiator. Look through the fins of the radiator from the front of the car. It should be clear of all debris. This includes the condenser that maybe mounted in front of the radiator. If the radiator and condenser are clear of debris, and the cooling fan is pulling air through the radiator, the next thing to question is the clogging of the radiator. This can be checked by warming the vehicle up until the thermostat is open, driving the vehicle for a few blocks to get some air flowing through it, stop, turn the motor off and feel the radiator with your hand. Be careful the cooling fan doesn’t turn on. Honda’s will often turn on with the key off. You are feeling for cold spots in the radiator. They will be obvious. But keep in mind, the coolant enters from the top and exits out the bottom radiator hose, so the bottom of the radiator will be colder than the top indicating the radiator is doing what it should. If there are cold spots that are obvious, then the radiator is clogged internally. This is a very common symptom for Honda’s.

What happens when the A/C is on, is the condenser gets hot and adds more heat for the radiator to dissipate. If the radiator is clogged internally, it is unable to adequately cool at a stop because there isn’t enough air flowing through the fins. Without the A/C on, the condenser doesn’t get hot and the radiator has enough cooling capacity to do its job.

I would also recommend a thermostat and keep in mind, it often takes some experience with checking for cold spots in the radiator to identify them. So if you are uncertain, book one of our technicians to help your out with the diagnosis of you overheating issue. Once the fault has been pinpointed the mechanic can then perform the repair that is necessary.

Good luck.

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