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Old 01-29-2002, 01:43 PM
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Cooling fan always on


The cooling fan on my 89 420SEL is always whirling away, even with a stone cold engine after sitting overnight. Is there a way I can test the thermo-switch or coolant temp sensor (are they the same thing?) to see if itís bad? Also, if someone could tell me where itís at it would be helpful.

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Old 01-29-2002, 03:20 PM
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on the driver's side below rear of headlight on air conditioning lines close to rad is a two pole sensor (can't remember the color) the two wires coming from the sensor go to a plug. Unplug the connection - if the fan stops your sensor may be bad or you have a pressure problem in air conditioning. My 560 has reverse problem. I have to short the wires together to get the fan to come on. It is in winter storage now but will take up the troubleshooting this spring when it warms up (-35F today).
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Old 01-29-2002, 04:39 PM
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I'll try it when I have the time.
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Old 01-29-2002, 05:44 PM
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This problem is sometimes brought on by a trip to the car wash. The water can get into the sensor mentioned by a previous poster. Just a possibility.
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