Radiator cooling fans
07-14-2007, 12:52 PM
#1
Racer
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Radiator cooling fans
In the past these fans would come on when the engine was warm or ac on and would run for a little then stop after the engine was turned off. Now all of a sudden they will stay on for a few minutes even if the car is started from cold and only run for a couple of minutes.
Temp gauge is working as it always has and the car is Not running hot. Is this new behavior really normal?
If not where would I check first?
In the 6 yrs I've owned this car the fans have never behaved this way. Fans would come on with AC.
Fans would run after shutdown when run hard(esp. in the summer).
Moved the cold car 30 ft to rinse off, engine ran for maybe 90 sec. fans ran for maybe 5 min after shutdown. Same thing happened after rinse and putting it away.
All temp sensors except bottom of rad were replaced since I've owned.
What would be telling the controller to cool it down?
Thanks
Temp gauge is working as it always has and the car is Not running hot. Is this new behavior really normal?
If not where would I check first?
In the 6 yrs I've owned this car the fans have never behaved this way. Fans would come on with AC.
Fans would run after shutdown when run hard(esp. in the summer).
Moved the cold car 30 ft to rinse off, engine ran for maybe 90 sec. fans ran for maybe 5 min after shutdown. Same thing happened after rinse and putting it away.
All temp sensors except bottom of rad were replaced since I've owned.
What would be telling the controller to cool it down?
Thanks
Last edited by Ed Taylor; 07-14-2007 at 08:34 PM. Reason: To add info
07-15-2007, 04:44 AM
#2
Chronic Tool Dropper
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After the key is off, the switch at the top of the intake manifold and the auto trans fluid temp switch are the only two things that will cause the fans to run. With the key on, that radiator temp sender and the two switches mentioned above are the only thing that should run the fans. If the AC button is pressed, then AC high-side pressure is added to the equation too.
07-15-2007, 05:53 AM
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The thermal sensor on top center of the S4 intake manifold is a reasonably common failure: next time the fans click on unexpectly, pull one of the wires off to confirm. If the fans stop, replace the sensor.
07-16-2007, 05:23 PM
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Racer
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Well it looks like it may be the Intake temp switch. If I unplug it the fans stop. Hmmmm. I replaced this in the first few months of ownership 6 years ago. Kinda short life for such a simple part don't ya think.
Before I spring for a new one can't I test this one for ohms and make sure it is bad?
Before I spring for a new one can't I test this one for ohms and make sure it is bad?
Last edited by Ed Taylor; 07-16-2007 at 05:41 PM.
07-16-2007, 06:38 PM
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Chronic Tool Dropper
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You could check but... It's a switch, so the resistance will be near zero, or it will be infinite/open. You've demonstrated that it is not open. 
The switch seems to have a bit of sensitivity to water. I did some engine cleaning, and a week later the fan was running too much after shutdown. By the end of the second week, it was always causing the fans to run. The old one was still pretty too! But a new one works correctly. Moral-- Cover or remove that switch before getting water anywhere near this thing.
The switch seems to have a bit of sensitivity to water. I did some engine cleaning, and a week later the fan was running too much after shutdown. By the end of the second week, it was always causing the fans to run. The old one was still pretty too! But a new one works correctly. Moral-- Cover or remove that switch before getting water anywhere near this thing.