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 on..car 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.

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・Fair and transparent pricing

Get a quote

What others are asking

Q: When I start my car, it shakes and smells like gas.

You could be getting a fuel smell from a fuel leak, or you might be getting a raw gas smell in the exhaust. Since you seem to have a misfire, I think you might be smelling it in the exhaust....

Q: Car exhaust leak

Since the vehicle is over ten years old, your exhaust system may be having problems with the gaskets or donut seals at the exhaust manifold or at the catalyst. My recommendation would be to have a mechanic, such as one...

Q: When A/C is on, the car overheats

Engine overheating with AC on is generally caused by one of two possibilities. One, is increased engine load caused by a failing AC compressor. The AC compressor adds rotational load to the engine and if the compressor is wearing and...

Related articles

P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...
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...