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Old 05-16-2007, 10:31 PM
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Join Date: May 2007
Posts: 1
electric fans going wild

on my 91 103 eng 124 body anytime the outside temp is above 60 deg when I start the car both fans come on,sometimes they come on by just turning the key to on. I have no idea where to start.I inspected my aux fan relay ,it looks ok so does the ceramic resistor. Pls help Thanks

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Old 05-16-2007, 11:04 PM
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Join Date: Jan 2005
Location: St. Louis Missouri
Posts: 473
Don't know if your car is the same as mine (95 E320)--if so, one of two things make the fans come on. 107C coolant temperature or refrigerant pressure of about 22 bar. Coolant temp is provided by a thermistor, ac pressure info is provided by a pressure switch. If either the pressure switch or thermistor are faulty, it could result in fans coming on when they should'nt.... Also, it could be a shorted relay but you said the relay was OK. (My vehiclew has two relays, one for temperature activation of fans, and one for ac pressure activation of fans)

If the temperature is less than 60, do the fans come on shortly after startup, or do they stay off?

Last edited by J. M. van Swaay; 05-16-2007 at 11:10 PM.
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Old 05-17-2007, 12:02 AM
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Join Date: Aug 1999
Location: Florida / N.H.
Posts: 8,804
Check the connector at the blue 2 wire sensor..if there is an poor connection there [ common] , the N22 module defaults to running fan
[ engine overheat protection circuit].
Second test is next time it does it, disconnect the pigtail wires at the pressure sw ..if fan stops , pressure sw is bad.

It will make it much easier to diagnose if you tell us if it is a High speed fan or low speed fan.
The blue sensor is in the high circuit, the pressure sensor is in the low speed circuit.

Last edited by Arthur Dalton; 05-17-2007 at 12:12 AM.
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Old 05-17-2007, 03:15 AM
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Join Date: Jul 2004
Posts: 187
Check temperature sensor on the 104 engine it's on the waterpump housing on the 103 engine I don't now.

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