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Old 01-29-2012, 06:59 PM
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cooling system

have a 2000 montana, the fans will only operate if you turn on the ac. sometime you can turn ac off and they will still operate till shut off or next driving cycle. with ac on always then they run as needed, from slow to high speed. ideas???

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Old 01-30-2012, 05:02 AM
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Might be the ac cut-in relay sticking or going bad. Just a guess tho'
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Old 01-30-2012, 07:44 AM
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Quote:
Originally Posted by cdmiller
have a 2000 montana, the fans will only operate if you turn on the ac. sometime you can turn ac off and they will still operate till shut off or next driving cycle. with ac on always then they run as needed, from slow to high speed. ideas???
Temp sensor. put a scan tool on it and see what the ecm thinks the engine temp is. Could also possibly be a bad relay, some vehicles use a seperate relay for fan control from temp and A/C activation
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Old 01-30-2012, 05:22 PM
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For what it's worth, I had the same problem on an '01 Ford - Radiator fan only came on with the AC. Turned out that they used a resistor similar to a heater blower resistor (only larger), to get the fan to run in it's low speed mode. My resistor was fried, so the only time the rad fan would work was in high mode. Furthermore, on my car, the ECU would never 'tell' the fan to run on high based on engine temp, even when it was in excess of 250 degrees. In my case, the only time the fan ran on high was when the AC 'requested' it to.

My rad fan speed resistor was mounted in the radiator fan shroud and was very easy to change.




There's a good chance that GM wires their radiator fans completely different than Ford does, but since the symptom sounded similar, I figured I would throw it out there for consideration.

It would be an easy thing to check.

Hope this helps....

Joe G.
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