'79 300D vacuum/heater box thing

As per advice from one of the techs here, I located the black box thing behind the right headlight under the hood. It sits on top of a junction of 3-4 vacuum hoses. On top it has a rectangular device with numerous wires plugged into it. Is this the vacuum pump that opens and closes the vents and lets heat/cold air into the cabin? Can it be easily removed, tested and replaced/repaired if necessary? As I mentioned in an earlier post, my blower motor runs strong, the system blows hot air on DEF. only, with no activity on hi-auto, low-auto, or bi-level, and no air conditioning, although I can hear a switch go on and off under the hood when I turn the air button to "on-off".

I hope this isn't TOO confusing.

Thanks,
Joe

I think you are in way over your head. Take this to a mechanic who is familiar with these and stick with doing whatever it is you do best. These systems can be very confusing and complex if you don't work on them daily. Think of this as a burden taken off of your shoulders I hope! Good luck with the repair.


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Benzmac:
ASE CERTIFIED MASTER AUTO TECHNICIAN
LEAD TECHNICIAN FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

The system is an old CHRYSLER design!! The system needs vacuum to operate. If the blower doesn't run on any speed other than defrost I'll bet you there is a vacuum leak! The most common leak is around the battery.

Have fun(no body else has)!!!!