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.

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

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: Catalytic shows not ready

Hi, thanks for writing in. The blinking light means you most likely have a misfire in one or more cylinders from an oil leak, from the valve cover getting on spark plug boots and shorting the cylinder out. The valve...

Q: Radiator leaking and overheating.

Hello, A coolant leak needs to be repaired sooner than later, as overheating can lead to engine damage. You will probably need the aid of a mechanic, such as one from YourMechanic, who can pressurize the system with a hand...

Q: Fan stays on when car off

The blower motor resistor seems to be a common repair on your car. It can cause the blower motor to run when the key is off. The heat and AC and your car has a dedicated computer. It also could...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...
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.