Radiator fan never turns on?

STEVE HAN

MEMBER
2003 TOYOTA COROLLA
1.8L
4 CYL
2WD
AUTOMATIC
160,000 MILES

The fan never turns on when I'm at a drive thru or a red light for too long. The car will overheat. I've changed radiators, I installed a new engine coolant temperature sensor, I replaced the fan motor, the 5-pin relay, and I can't figure out why the fans won't turn on. The fan will work if I bypass and plug it straight into the battery. I did notice the last time I took the coolant out there was a lot of oil in there. Not sure if that's related. Also, the wiring to the fan only has one wire. Fan does not turn on when the ECT sensor is disconnected.

3 Replies

KEN L

MASTER CERTIFIED MECHANIC
42,840 POSTS

The fan motor needs two wires so it will work, here are the wiring diagrams so you can see who the motor should be wired. Please check the images below. Also check for power at the fuses in the diagrams as well.

This guide can help:

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

Check out the images (below). Please let us know what you find. We are interested to see what it is.

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Monday, March 27th, 2023 AT 10:46 AM

STEVE HAN

MEMBER
2 POSTS

Thanks for your reply. It looks like the ECU-IG fuse is dead. I switched it with a spare 10A fuse, and it also does not light up. What is the next step?

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Monday, March 27th, 2023 AT 6:32 PM

KEN L

MASTER CERTIFIED MECHANIC
42,840 POSTS

That is power by the IG1 relay which is located in the fuse panel on the left side of the dash, I would swap it out to see if that fixes the problem, please let me know. Check out the images (below). Please let us know what happens.

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