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Old 01-03-2003, 02:53 AM
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Join Date: Nov 2002
Location: Austin, Texas
Posts: 179
91 350 SD Auxillary fans problem

I live in Canada where is very cold, after car is running for about 5 minutes the auxillary fans come on and keep running all the time .
Temperature here is -20c (approx -4f ) or even colder.
What could be the problem?

Thank you
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Old 01-03-2003, 01:10 PM
Join Date: Mar 1999
Location: Tucker, Ga USA
Posts: 12,153
On the engine at the front there is a BLUE 2 pin temp switch that controlls the aux fans. This switch is a very common failure. IF you try to un-plug or jump to by-pass, the fans will still run. You will need to replace the switch or subsitute at least 500ohm resistance to turn the fans off OR remove the aux fan relay.
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Old 01-03-2003, 07:53 PM
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Join Date: Nov 2002
Location: Austin, Texas
Posts: 179
What should be the resistance on the switch when cold and in good condition.?
I did a test , removed the connector from the switch and shorted the wires that were comming to it, the fans came on right away, is this an indication that the switch is bad?

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