Skip the auto shop - Our mechanics make house calls

Q: Cooling Fans

asked by on

What makes the cooling fans kick on only when the AC is turned on ? My fiancee's car is overheating when the AC is not on. I have replaced the radiator hoses and thermostat previously and just replaced the coolant temp sensor today. What else could it be causing this ?

My car has 137000 miles.
My car has an automatic transmission.

The engine fans should turn on based on engine temperature. If the sensors you just replaced are not connected properly, it would cause them to fail. When repairs have been made recently, always verify they are holding. Have you checked the water pump? If it is not pushing enough fluid through, the cooling system will not function.

Assuming the coolant is topped off and in good condition (old coolant has a lesser heat transfer properties), you may want to look into the fan clutch which controls the fan. This is usually replaced with the water pump. The other component you should consider is the drive belts. If the pulleys or the belt have failed, the accessories will not work correctly.

If you need to have this repaired, consider YourMechanic, as one of our mobile technicians can come to your home or office to diagnose your overheating issue firsthand.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: I hear a grinding when braking.

A grinding sound when braking could be an indicator of low pad material or shoe material depending on whether the grinding is coming from the front or rear axle. The sound may also be worn or damaged braking hardware. Either...

Q: AC air coming out defrost channel

This is an indication that the mode door actuator within your dash has gone bad. This actuator is responsible for moving the door that allows or blocks off air flow to a certain vent location. Sometimes this part can be...

Q: Checking transmission fluid on 2002 Ford Explorers

Yes, the engineers have chose to go that way. They want to keep it so you can go to them. There's a very complicated way to check the fluid. You need all kinds of tools and special equipment. They are...

Related articles

How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
P2428 OBD-II Trouble Code: Exhaust Gas Temperature Too High Bank 1
P2428 code definition A P2428 trouble code signifies that the PCM has detected a problem in the exhaust gas temperature sensor circuit in bank 1, which subsequently contains the number one...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.