I have a non working cooling fan

Tiny
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!
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Sunday, August 16th, 2009 AT 5:03 AM

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Tiny
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
Tiny
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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
Tiny
JDL
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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
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
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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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Monday, May 13th, 2019 AT 7:31 PM

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