I have a non working cooling fan

PAGECOUNTYMALE

MEMBER
1999 CHEVROLET LUMINA

I have a non working cooling fan, I have changed the relays(3 of those), changed the engine temperature sensor, checked for bad wires also. I can get the fan to run by holding the breaking point in the reply with a screwdriver, but it won't work on it's on, it has duel fans, but to my understanding only one fan supposed to cool the engine without the air conditioner running? I am in need of advice to what it might be that the cooling fan won't work on it's own like it's supposed to, I have currant at the sensor, current at each relay from the PCM, but still it won't work, any suggestions will be greatly used, thanks!

4 Replies

JDL

MECHANIC
16,098 POSTS

This sounds like you have a fuse out #3 fan fuse 25 amp but to be sure here is a guide to help you check the fuse with the location in the diagrams below I also included the cooling fan wiring diagrams so you can see how the system works.

https://www.2carpros.com/articles/how-to-check-a-car-fuse

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

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Monday, May 13th, 2019 AT 7:31 PM

PAGECOUNTYMALE

MEMBER
6 POSTS

I Am trying to figure out why the relays ain't tripping and sending the current to the fans, I have a green, yellow and black wires at the temperature control sensor, the green is hot, the yellow is not or the black. I seen in a Haynes manual that black is ground, yellow goes to control modular, and green comes from the temperature gauge, so I Assume the green is current into the sensor. I Am lost as why or what's preventing these fans from working correctly. Any suggestions will be useful, is it possible that the ground is weak, causing system failure?

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Monday, May 13th, 2019 AT 7:31 PM

JDL

MECHANIC
16,098 POSTS

It sounds like the computer isn't grounding the relays for some reason? On some models, if you unplug the coolant temp sensor, turn the key on, the fan/s will run.

You need a digital multimeter, with that sensor unplugged and the key on, the yellow wire has around 5 volts? Anything on the black wire?

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Monday, May 13th, 2019 AT 7:31 PM

KEN L

MASTER CERTIFIED MECHANIC
47,643 POSTS

Hello,

You must have a wire that is not getting a good connection or a relay is not working correctly, here is a cooling fan wiring diagram (below) you can use for testing and a guide that will show you how to get the problem fixed.

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

and

https://www.2carpros.com/articles/how-to-check-wiring

Please run some tests and get back to us so we can continue helping you.

Cheers, Ken

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