Cooling fan(s) always runs when key turned but car not running
02-27-2003, 12:35 AM
#1
Track Day
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Cooling fan(s) always runs when key turned but car not running
I have a 1987, 5-speed.
I just had a whole mess of work done by a great mechanic : T-belt and water pump, new harmonic balancer (old was cracked), front cam seals, main seal, valve cover gaskets, oil fill neck gasket, knock sensors replaced, injectors flowed and balanced, new rotors, caps, and wires, intake manifold and valve covers power coated).
Car runs awesome. It always did, but now it's even happier. But the fan always runs if the ignition is turned on. Regardless of whether the car is hot or cold, and even if I never crank it up. The A/C button can be depressed or not, doesn't matter.
I don't recall this mode of operation before. Is this the correct behavior, or did something happen. If so, what's the likely issue. I know the radiator had to come out for all the work.
The mechanic was great - Jeff at Sportscar Workshops in Richmond VA. I'm just tired of pestering him, and don't want to bother if it's not an issue.
Thanks in advance,
Ben Thorp
I just had a whole mess of work done by a great mechanic : T-belt and water pump, new harmonic balancer (old was cracked), front cam seals, main seal, valve cover gaskets, oil fill neck gasket, knock sensors replaced, injectors flowed and balanced, new rotors, caps, and wires, intake manifold and valve covers power coated).
Car runs awesome. It always did, but now it's even happier. But the fan always runs if the ignition is turned on. Regardless of whether the car is hot or cold, and even if I never crank it up. The A/C button can be depressed or not, doesn't matter.
I don't recall this mode of operation before. Is this the correct behavior, or did something happen. If so, what's the likely issue. I know the radiator had to come out for all the work.
The mechanic was great - Jeff at Sportscar Workshops in Richmond VA. I'm just tired of pestering him, and don't want to bother if it's not an issue.
Thanks in advance,
Ben Thorp
02-27-2003, 04:37 AM
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Burning Brakes
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Ben,
Two sensors are controlling the fan - The A/C pressure sensor and the thermo-switch in the radiator - Simply try to disconnect them one by one.
I would start with the thermo-switch in the radiator (down-left-front of the radiator)
Two sensors are controlling the fan - The A/C pressure sensor and the thermo-switch in the radiator - Simply try to disconnect them one by one.
I would start with the thermo-switch in the radiator (down-left-front of the radiator)
02-27-2003, 07:55 PM
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Chronic Tool Dropper
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On the S4, the temp switch on the top of the intake will cause the fans to run as Mark says. On mine that sensor is erratic (probably has water in it), and it causes the fan to run sometimes even with the key off. Diagnostic method: disconnect the wires from the switch (brown and gree/brown IIRC)and see if the fans stop. Remember that the hood safety switch on the right fender needs to be depressed for the fans to run.
Second cause of fan run is the temp sensor. This sensor reads the temp and controls the speed of the fans. Hotter = faster (three speeds), and the same sensor also controls the flap position (3 positions) on your car. Hotter = more open.
There's a pressure sensor on the AC system, a little cannister about 2" dia and 2" long, attached to the AC piping at the drier, right side in front of the radiator. Two black thumb-nuts on mine hold the wiring to it. More pressure = Fan run and flaps open. Disconnect and insulate those wires, fan should not run.
Those are the three functions documented in the manual. Others have also mentioned that there's a failure mode in the final controller that will cause one fan to run all the time if the other fails. Making an assuption that the "fail" definition includes having a fan disconnected/not working, you can look to see if the always running condition is both fans or just one. If it's just one, turn the key off to stop the fans, and reach down behind the fans looking for a connector loose at a fan motor. The wiring harness runs from the right side just behind the radiator sheet, down the top right fan-motor strut or support brace behind the right-side fan, splits there to the two motors. The right side motor lead wraps down and comes back up under the rear of the motor, where it plugs in at the motor itself. The left-side motor lead continues down after the split, and bends to the left towards the left fan underneath, then follows the brace there back up to where it plugs into the left side fan. Best bet might be to pull and reseat electrical connectors on both fan motors to be sure.
Remember that the "left" and "right" references are based on sitting in the driver seat; "left" is driver side on US cars.
The FSM offers a detailed troubleshooting procedure for the two controller modules, probably unneeded in your case. Most likely candidate/easiest to diagnose are the switch on the intake per Mark, and the fan motor plugs. My nickel leans towards the fan motor plugs, since your wrench is sure to have removed/disturbed them as part of the T-belt/WP replacement.
Please let me know what you find.
<img border="0" alt="[typing]" title="" src="graemlins/yltype.gif" />
Second cause of fan run is the temp sensor. This sensor reads the temp and controls the speed of the fans. Hotter = faster (three speeds), and the same sensor also controls the flap position (3 positions) on your car. Hotter = more open.
There's a pressure sensor on the AC system, a little cannister about 2" dia and 2" long, attached to the AC piping at the drier, right side in front of the radiator. Two black thumb-nuts on mine hold the wiring to it. More pressure = Fan run and flaps open. Disconnect and insulate those wires, fan should not run.
Those are the three functions documented in the manual. Others have also mentioned that there's a failure mode in the final controller that will cause one fan to run all the time if the other fails. Making an assuption that the "fail" definition includes having a fan disconnected/not working, you can look to see if the always running condition is both fans or just one. If it's just one, turn the key off to stop the fans, and reach down behind the fans looking for a connector loose at a fan motor. The wiring harness runs from the right side just behind the radiator sheet, down the top right fan-motor strut or support brace behind the right-side fan, splits there to the two motors. The right side motor lead wraps down and comes back up under the rear of the motor, where it plugs in at the motor itself. The left-side motor lead continues down after the split, and bends to the left towards the left fan underneath, then follows the brace there back up to where it plugs into the left side fan. Best bet might be to pull and reseat electrical connectors on both fan motors to be sure.
Remember that the "left" and "right" references are based on sitting in the driver seat; "left" is driver side on US cars.
The FSM offers a detailed troubleshooting procedure for the two controller modules, probably unneeded in your case. Most likely candidate/easiest to diagnose are the switch on the intake per Mark, and the fan motor plugs. My nickel leans towards the fan motor plugs, since your wrench is sure to have removed/disturbed them as part of the T-belt/WP replacement.
Please let me know what you find.
<img border="0" alt="[typing]" title="" src="graemlins/yltype.gif" />
