Cooling fan will not come on

LRADENHEIMER

MEMBER
1992 CHEVROLET CAMARO
5.0L
V8
AUTOMATIC
108,000 MILES

Cooling fan does not come on as should. With A/C on the fan comes on. If I ground at the thermal switch on engine block it still does not work. If I ground the green wire on the relay the fan runs fine. There looks like there is an ECM module in front of the fan relays. Does the thermal sensor run through this module? Any ideas?

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Saturday, May 12th, 2018 AT 9:49 AM

15 Replies

ASEMASTER6371

MECHANIC
52,797 POSTS

Good afternoon.

The coolant temperature sensor is the control for the fan. If you remove the connector while the key is on, it should send a signal of high temperature to the PCM and the fans should kick on.

Check that and see if it happens.

Roy

https://www.2carpros.com/articles/symptoms-of-a-bad-coolant-temperature-sensor

https://www.2carpros.com/articles/how-an-electric-cooling-fan-works

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Saturday, May 12th, 2018 AT 10:32 AM

LRADENHEIMER

MEMBER
8 POSTS

I disconnected the sensor and the fan did not come on. My car only has one fan. The sensor is located by the starter on the block is it not. The one by the manifold on driver side is just for the gauge I thought.

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Saturday, May 12th, 2018 AT 10:47 AM

ASEMASTER6371

MECHANIC
52,797 POSTS

Do you have a voltmeter to do some checks?

Need to check voltage at the relay to be sure power is available for the fan to run.

Roy

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Saturday, May 12th, 2018 AT 10:51 AM

LRADENHEIMER

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8 POSTS

I did check the voltage and it is there on the relay. The only way I could get the fan on was to ground the green and white wire on the relay and the fan would come on.

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Saturday, May 12th, 2018 AT 10:56 AM

ASEMASTER6371

MECHANIC
52,797 POSTS

Okay, I would replace the coolant temperature sensor.

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Saturday, May 12th, 2018 AT 11:41 AM

LRADENHEIMER

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8 POSTS

I replaced the coolant sensor and it did not help either.

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Saturday, May 12th, 2018 AT 1:03 PM

ASEMASTER6371

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Did you let it warm up to the temperature for the sensor to turn on the fan? It is about 212 degrees for it to turn on.

Roy

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Saturday, May 12th, 2018 AT 1:29 PM

LRADENHEIMER

MEMBER
8 POSTS

It got up to about 230 by the gauge and I turned the A/C on to bring the fan on to cool it back down.

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Saturday, May 12th, 2018 AT 1:49 PM

ASEMASTER6371

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What color are the wires on the coolant sensor?

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Saturday, May 12th, 2018 AT 1:54 PM

LRADENHEIMER

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Black and yellow.

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Saturday, May 12th, 2018 AT 2:00 PM

ASEMASTER6371

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That is the issue. The switch you need is on the head.

I attached the location of the switch.

Roy

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Saturday, May 12th, 2018 AT 2:03 PM

LRADENHEIMER

MEMBER
8 POSTS

I can see the wire. Why in the heck would they put it there. That will be tomorrow. I will have to get the car back up on jack stands to get to it. I cannot even get near it on top.

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Saturday, May 12th, 2018 AT 2:19 PM

ASEMASTER6371