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#1
11-04-2004, 11:56 AM
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Auxiliary Fans running always FULL speed
The auxiliary fans (dual) are operating at full speed as soon as the ignition is turned on my 400e 93 (m119 engine). I've checked the fuse, but not the relay. It is my understanding the "full speed" aux fan condition is normally caused by short or failure in the coolant temperature sensor creating the low resistance state. Since the fans are not operating at "half or low" speed, I'm NOT suspecting the problem is a result of a pressure sensor on the air conditioner.
Has anyone else had a similar issue? Could the "full fan speed" be a result of a failed auxiliary resistor or is a failed fan resistor characterized by other symptoms other than full fan speed? Should I begin by checking the ohms on the coolant temp sensor? Thanks for any help! Russell
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Russell McMahon Tulsa, OK 2001 CLK 320 1992 400se 1993 400e 2000 320ML 
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#2
11-04-2004, 12:11 PM
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Aux fan temp sensor is suspect. Check for OHMS.. also , be aware that it could also be bad connection at the the sensor as if the sensor is out of the circuit, the Module defaults to full fan.
Other possible is relay contacts stuck closed. Aux fan resistor is not in the aux HIGH fan circuit. It is only in low fan circuit[ that is how low fan is accomplished]
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#3
11-04-2004, 12:24 PM
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Arthur, Thanks for the response.
When you make reference to the “Aux fan temp sensor” are you referring to the coolant temp sensor on the engine block?
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Russell McMahon Tulsa, OK 2001 CLK 320 1992 400se 1993 400e 2000 320ML
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#4
11-04-2004, 12:34 PM
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Blue 2 wire , I believe
What chassis?
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#6
11-04-2004, 07:41 PM
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B11/2 is Engine management ECT sensor
It is two sensors in one case ..pins 1/3 and 2/4 should read ohms and they both should have the same values. But... the ECT sensor for the aux high fan should be B10/8... blue base , 2 wire...according to the schematic for 124.034 -1993 400E... The other single wire sensor is for temp Gauge........... Last edited by Arthur Dalton; 11-04-2004 at 10:52 PM.
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#7
11-04-2004, 10:50 PM
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Thanks for the info ... Just to clarify for the other forum viewers.. I think Aurthor meant ECT Sensor B10/8 - not D10/8.
Looks like values should be .... Temp K 20c 5.0-8.0 ohms 60c 1.0-1.5 ohms 85c .046-065 ohms 100c 0.3-0.4 ohms 120c 0.19-0.22 ohm I'll test tomorrow.
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Russell McMahon Tulsa, OK 2001 CLK 320 1992 400se 1993 400e 2000 320ML Last edited by rsmcmahon; 11-04-2004 at 11:02 PM.
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#8
11-04-2004, 11:00 PM
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Your values are way off
Move the decimal over a few.. or specify K ohms......
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#9
11-05-2004, 10:46 AM
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FYI.... Turns out ECT Sensor B10/8 checked out fine. As I was removing and connecting the connector, the auxiliary fans would turn on full speed then quit depending on which way I moved the connector wire.
Appears to be an "open" in the ECT Sensor B10/8 conneting wire.... The dreaded biodegradable wiring harness on the M119 engine is failing. Show me the money......
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Russell McMahon Tulsa, OK 2001 CLK 320 1992 400se 1993 400e 2000 320ML Last edited by rsmcmahon; 11-05-2004 at 12:17 PM.
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#10
11-05-2004, 04:39 PM
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aux fan switch
Check out part # 008-542-32-17 4 prong auxiliary fan switch pretty common failure call phil at partsshop 888 333-4642
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Linear Mode
