Skip the auto shop - Our mechanics make house calls

Q: Fan doesn't come on unless defrost is on.

asked by on

Fan does work just not unless the ac is would be hot but temp in the car would be fine no sign of overheating.

My car has 198000 miles.
My car has an automatic transmission.

A: Hi there. I am assuming you are referring t...

Hi there. I am assuming you are referring to the radiator cooling fan. If it works when the AC or defrost is on and not when the engine starts to warm up, then that can be a circuit issue or a temperature sensor problem. If the engine seems as if it is getting hot and the fan is not turning on, and the gauge is still showing cool, then the sensor is more than likely faulty.

I start by checking the sensor reading, and if it is fine, then I test the circuit. It can also be a relay problem, so the entire circuit will need to be tested. If you are planning on having the fan issue repaired, consider having a certified mechanic, such as one from YourMechanic, come to your home or office to determine if you need a sensor replacement.

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・Save up to 30%

Get a quote

What others are asking

Q: Leak in the brake line

Hello. With brakes being one of the more important systems on a vehicle, the vehicle should not be driven until it's repaired. I assume you know approximately where the leak is since you are seeing the result of the leak....

Q: Lights connected to the same fuse don't work

Hello. This is typically a failure in the headlamp switch or a bad ground connection. However, the most common issue I have found with this is the switch. I would typically start by accessing the back of the switch by...

Q: overheating at idle with new clutch fan

Inspect and verify that there is no plastic bag/trash on front of condenser or up between the radiator and condenser. Plastic ductwork around the fan are all present and intact. You should also consider whether the fan clutch an OEM...

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...
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.
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.