Radiator fan not working when a/c is on. mustang v8-5.0l ...

Q: Radiator fan not working when a/c is on.

asked by on August 02, 2016

Hello. Car does not overheats, cause I notice the fan running when car is at operating temperature, but when I turn a/c at cold setting, fan doesn't run. It's supposed to run when the a/c clutch is engaged. A/C system was checked and is fully charged and cabin gets cold when car is moving, but at traffic, or when car is stopped, air starts to blow warmer. I imagine the same fan has 2 speeds, but I need a way to troubleshoot the failure. I'm going to chek the relay today, but some people tell me this car has a control module for the fan operation? Don't want to damage parts, and the dealer is too far awai from me. Thanks in advance for any reply.

My car has 33000 miles.
My car has a manual transmission.

Your vehicle fan is controlled by two different relays in the engine compartment fuse box. One is for low speed and the other is for high speed. The ECM controls both of the relays. The wires to the cooling fan motor are black (ground) brown (high speed) green with white stripe (low speed). With the engine running and the A/C turned on, check for power getting to the low or high power wires to the cooling fan motor.

If you do not have power to the low power wire, then try to replace the relay first. You may be able to temporarily swap the high and low speed relays to test to see if fan is coming on with A/C on. If it does, then try and replace both relays since they may both be burnt. If you find you are getting power to the cooling fan motor but it is not turning, then you have a defective motor. If you do not have power and the relay swap did not work, then you will need to have the computer checked to see if its able to turn on and off the fan using a dealer scanner. The problem is most likely the relay or fan motor.

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