Cooling fan not working

Tiny
PAGECOUNTYMALE
  • MEMBER
  • 1999 CHEVROLET LUMINA
Electrical problem 6 cyl Front Wheel Drive Automatic 150, 00 miles

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

4 Replies

Tiny
JDL
  • EXPERT
Hello, the computer doesn't supply voltage to the fan relay, it supplies ground to the control side. The voltage circuits to the relay, there are two, are hot all the time. With relay 1 unplugged, I'm only talking about relay 1, use a testlite, how many hot terminals, should be two? You've probably already done this, I'm just trying to get it straight in my head.
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Sunday, August 16th, 2009 AT 10:42 AM
Tiny
PAGECOUNTYMALE
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Yes you are right there are two hot wires to the relays, I have tested those and have current, when I test the green or blue wires on relay one or two the fans will run, Iam just using an test blubb in an two wire socket as a tester. Iam 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 temperture 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 guage, so Iassume the green is current into the sensor. Iam 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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Sunday, August 16th, 2009 AT 5:17 PM
Tiny
JDL
  • EXPERT
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, August 17th, 2009 AT 8:54 AM
Tiny
KEN
  • ADMIN
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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Wednesday, May 31st, 2017 AT 5:17 PM

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