Put it on the supply side. The brown wire is the ground (car side).

Ok, so today, I replaced the aux pump, the blower and the acc (ccu?). No blower....I suspect that the ccu I got from ebay is bad. I don't know what else it could be.

BTW, the aux water pump took me about 1/2 an hour. I must be lucky. Everything came off easily and had no problems. The pump was frozen so I'm sure that I didn't waste my effort there. Had I known that I could just unplug the pump, I would have done that.

Send me a email if you are interested in a remanufactured Unit... Part numbers are 126 830 02 85 ... jim16671836@yahoo.com If the unit helps you, then you pay for it and if it doesnt help you just ship it back.. I have 3-4 units with different part numbers for a 126.... Jim

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James A. Harris

The seller I bought from said he will cross ship me a new unit. I'll check the motor just in case.

You need to determine what part isn't working.

Start with the blower motor. You can either apply 12 volts to the connector and see if it spins, or check the voltage at the connector with the CCU in defrost mode.

If the motor works and there is no voltage at the connector, then the problem is either the CCU, the blower motor module, the temperature control module, or a fuse. I don't have any of the schematics in front of me to help diagnose any of these.

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Michael LaFleur

'05 E320 CDI - 86,000 miles
'86 300SDL - 360,000 miles
'85 300SD - 150,000 miles (sold)
'89 190D - 120,000 miles (sold)
'85 300SD - 317,000 miles (sold)
'98 ML320 - 270,000 miles (sold)
'75 300D - 170,000 miles (sold)
'83 Harley Davidson FLTC (Broken again) :-(
'61 Plymouth Valiant - 60k mikes
2004 Papillon (Oliver)
2005 Tzitzu (Griffon)
2009 Welsh Corgi (Buba)

Has anyone continued investigation of this problem?
I came across this thread recently through a search, after my car started blowing the #8 fuse-25A labelled heater blower. I think you guys were talking 126 dialect though, my 123 seems to be slightly different. It will blow a new fuse after 2-3 seconds, so it doesn't seem like it's a direct short. I have also proven the blower itself to be good on the workbench (20 amp fuse holds), and after consulting wiring schematics, unplugged the aux water pump but have not retested the circuit yet...

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'83 300D Turrrbo 295K miles

While the CCU can certainly be NG, the system uses a blower controller and a set of resistors to control the fan speed, in addition to the CCU. Either of these items can also be the culprit, although they are less likely to fail.

I've already replaced the fan relay. I did that first before I knew the system. I have not replaced the resistor pack but I really suspect the acc. Electronically, I don't think there's much more to the system......