pifcat2

First symptom was blowing warm air at any setting, second was continually blowing #7 fuses. I replaced the CCU with one from an '87 and the blower seems to work properly and the fuse doesn't blow anymore. I checked the 134a with a can with a gauge and doesn't indicate low but it says to "take it to a specialist." Before I do, I'd like to eliminate some possible faults.

Voltages:
key to Acc: 0V
key to far right: 12V
Engine running, no fan: 3V
Engine running, fan on: 13.65V
Engine running and wheel turned to max hot, fan low & high: 13.4V
Engine running and wheel turned to max cold: 4V +/- .20V
Engine running button to defrost: 4.2V

I can feel constant warm hoses to and from the heater core. I applied 12V to the heater valve and aux pump and both appear to operate (click at valve and motor running at pump). Both get power when the ignition was switched.

An earlier symptom was clicking under the dash. I believe vac pod(s) are blown but haven't checked them with a vac pump yet.

hellspcangel911

i had the same problem on a 87 300td, ended up replacing the climate controller it was 400$ for the part, plus some silicone tubing to replace some of the old vac lines with while i had it out, but it fixed the issue.
Are you getting warm air or hot air?

Brian_I.

Have the same issue with Hot air rising from out of the defroster ports. Changed the CC panel to no avail.

hellspcangel911

try bypassing the heater core

its probably the mixer valve solenoid is stuck

Brian_I.

Can you give any more info on this? I have no idea what that means but I'm willing to give it a try.

Thank you!

hellspcangel911

give this a try
http://forums.mercedesclub.org.uk/sh...d.php?p=350116