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  #1  
Old 05-23-2019, 01:48 PM
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w124 87 300d

My aux cooling fan runs constantly. I am sure I have read here before about this so my apologies for opening another thread. One of the sensors is obviously not functioning. And btw, it runs constantly whether the a/c is on or not.
Thanks.
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  #2  
Old 05-23-2019, 01:52 PM
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Should be a sensor on the drivers side under hood near the headlight on the frame rail. Two wires. Fan should turn off when unplugged.

I can take a pic when I get home this afternoon.
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  #3  
Old 05-23-2019, 02:04 PM
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Sounds like the temperature switch has failed closed. Trace the upper radiator hose back to the head, shortly after the rubber stops and the metal starts, there is a sensor with two or three wires. Pull a wire or two and the fan should shut off.
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Old 05-23-2019, 02:40 PM
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Switch would be failed open. Pulling those two wires makes the fan come on. Might have to pull the relay or pull the plug for the fans. Right next to the ac dryer behind the driver headlight.
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  #5  
Old 05-23-2019, 06:45 PM
WTB: 94/95 E320 Wagon
 
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Quote:
Originally Posted by Phillytwotank View Post
Switch would be failed open. Pulling those two wires makes the fan come on.

On my '87 wagon, I have to short across the temperature sensor I described in order to make the aux fan run. The switch would have to fail closed.



Looks like on later cars, your method should work. Any break in the circuit between the sensor and the PBU would cause the aux fan to run.
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'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC
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