Mechanics

MY COOLING FAN ONLY RUNS WITH THE A/C ON

1987 Buick Century • 83,000 miles

I recently acquired a 1987 Century with the 2.5L engine. The car runs great however the cooling fan only runs with the A/C on. I checked a basic wiring diagram and find that the wire from the ECM to the fan is grn/yellow. There is a plug near the fan hanging in space that has two wires: grn and grn/yellow. The problem is I can't find a home for it. The plug that goes on the fan has a blk and blk/red wire and there are no other plugs. I even checked at the parts store to see if it had the wrong fan and no it apparently has the correct fan. Traced the black and red wire up the harness a bit looking for another plug but no luck. Any suggestions?
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Csm1992
September 25, 2012.



Does your temp gauge work?Also do you have a multimeter to do some testing?


Saturntech9
Sep 25, 2012.
Check the coolant fan switch located on upper left side of engine, at end of exhaust manifold. It has a Dark Green/White wire.


KHLow2008
Sep 25, 2012.
I am an above average shadetree mechanic and have tools etc. The plug in question has grn and grn/yellow wires. The coolant temp sensor has one wire attached.


Tiny
Csm1992
Sep 25, 2012.
Post a pic of the connector showing it and where its located. The single wire is the gauge the two wires is the coolant temp sensor connector


Saturntech9
Sep 25, 2012.
It says the temp sensor is on left side of engine bellow coolant outlet.


Saturntech9
Sep 25, 2012.
Find the fan relay try swapping the relay with another 1.I would replace the coolant sensor that is what controls the fan oper. It grounds the fan relay to turn the fans on when the a/c is off.


Cadieman
Sep 25, 2012.
If the fan comes on with the ac I would say the fan relay is working wouldn't you cadieman?


Saturntech9
Sep 25, 2012.
Yes but the coolant temp. Sensor tells the cpu when to turn the fans on when the temp. Is to high. The fans are turned on auto. As soon as u turn the a/c on.


Cadieman
Sep 26, 2012.
Correct but the same relay is used to turn the fan on at the correct temp or when the ac is turned on. So when you said to check the relay that's why I said what I said.


Saturntech9
Sep 26, 2012.
I was thinking the a/c grounds the relay directly from the a/c head when turned on. When u let the sensor ground the relay thats from the temp. Sensor. So u have 2 circuts controlling the fan funshion by grounding the relay.1 is the cts and the other is the a/c head. Seeya tomarrow im falling asleep. Ltr


Cadieman
Sep 26, 2012.
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