Cooling fan not kicking on?

DEVYN PROVINS

MEMBER
2010 MAZDA 3
2.3L
4 CYL
2WD
MANUAL
176,252 MILES

Pulled the engine a while ago to rebuild it and when we put it back in and started it, we noticed that when the vehicle exceeded temperature the fan would fail to kick on. Replaced the fan control module, the coolant temperature sensor and the capacitor that goes on the end of the fan control module and the fan still fails to kick on. I did notice that when we unplugged the coolant temperature sensor while the car was running the fan kicked on to the highest setting. I want to add that the A/C compressor does not work and does not have a belt. But that's an issue for a different day unless that is causing the problem.

1 Reply

KEN L

MASTER CERTIFIED MECHANIC
48,323 POSTS

It sounds like you may have a faulty PCM. Here are the cooling fan wiring diagrams so you can see how the system works with a guide to test the wiring connections. If the wiring is okay replace the PCM. You can get a preprogrammed unit by searching Google or Ebay. You can confirm the failure by doing a CAN, you can get a CAN scanner (Controller Area Network) which will work on most cars from Amazon.

Here is a video to show you how:

https://youtu.be/u-4syLc-ifQ

and

https://www.2carpros.com/articles/can-scan-controller-area-network-easy scan Check out the images (below). Please let us know what happens.

Images (Click to make bigger)