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My car:
C280 2007 sedan 4matic
What happened:
When the car is started, and the AC is turned on, the fan won't come on.
When the car is driven, and the temperature gauge gets a bit above 80F, the red coolant temperature warning light (shown on bottom of message) comes on and the needle of the temperature gauge slightly drops to just under 80F.
The electric fan will not come on then either.
What I have done so far:
I checked the user manual for the display symbol, and it tells me that the cooling fan is malfunctioning and to replace it.
I have checked fuse 54, and it is good.
I have hooked up my scanner (Foxwell NT530) and did a live test on the fan at anywhere from 20% to 90% and the fan didn't come on.
I have removed the fan from the car and tested the fan connector plug,
Results when car ignition is off or during live test with the scanner:
I get 12V/DC on the bottom two larger pins
No voltage from the black wire
No voltage from the green wire
I have removed the fan from the car and tested the fan by giving it steady 12V (bottom left +,bottom right - when looking at the fan plug) and 12V on the black wire (the top right).
Result: Fan started spinning.
My questions:
When I hook up my scanner and do a live test on the fan, should it bypass all other controls (AAC control and operating unit, temp sensor, pressure sensor, ME-SFI control unit, etc.), and turn on the fan via the front SAM control unit and give the black wire voltage?
If yes, where is that black wire (with white stripe) connected to the SAM so I can check it for continuity?
Anything else I could do to diagnose the problem?
Thank you all for reading and helping.
Last edited by GorillaCoala; Aug 13, 2022 at 04:35 PM.
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