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.

__________________
DS
2010 CL550 - Heaven help me but it's beautiful
87 300D a labor of love
11 GLK 350 So far, so good
08 E350 4matic, Love it.
99 E320 too rusted, sold
87 260E Donated to Newgate School
www.Newgateschool.org - check it out.
12 Ford Escape, sold, forgotten
87 300D, sold, what a mistake
06 Passat 2.0T, PITA, sold

Las Vegas NV

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.

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.

__________________
Respectfully,
/s/
M. Dillon
'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

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.

__________________
Current fleet
2006 E320 CDI
1992 300D - 5speed manual swapped

former members
1984 300D "Blues Mobile"

1978 300CD "El Toro"

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.

__________________
Respectfully,
/s/
M. Dillon
'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