I am changing oil tomorrow so voltage probe is my next step.
So far, the CCU readout has reflected what is happening with fans, refrigerant pressure, and evap temp, albeit with a delay of a few seconds. Evidence leans more towards a faulty fan but I would not be surprised if it is the controller.
Quote:
Originally Posted by Diseasel300
If the fans aren't running, the head pressure climbs to the point it trips the high pressure cutout when you're idling. That's likely why you were getting the oscillating temps when the fans didn't run.
Not sure how you're getting 21V to the fan when you're running a 12V system. Perhaps the values given are PWM steps and not volts.
The only way to really tell what's going on is to probe the voltage going to the fan motor with a voltmeter and see what's actually happening. If you have voltage at the motor, but it isn't spinning, you know the motor is the problem.
If you see the CCU has the fan set wide open but you have no voltage at the fan motor, you know the problem is in the communication line or the fan motor controller.
All the CCU readout is telling you is what it thinks its doing, not what's actually happening. If you have an open connection somewhere or the motor controller is bad, the numbers on the display are meaningless.
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2008 E350 4matic / Black/Anthracite
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Gone but not Forgotten:
2001 E430 4matic, 206,xxx miles, Black/Charcoal
1995 E320, 252,xxx miles, Black/Grey
1989 260E, 223,00 miles, Black/Black
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