A/C and heater inoperative

LEEBK

MEMBER
1990 MERCEDES BENZ 420SEL
V8
2WD
AUTOMATIC
210,126 MILES

I have no heat or A/C. I have replaced the mono valve, condenser, compressor and climate control, and nothing has changed. What else could be wrong?

Tuesday, July 17th, 2018 AT 10:54 AM

3 Replies

KEN L

MASTER CERTIFIED MECHANIC
48,363 POSTS

Can you explain? So you do not have any air coming out or the cold and hot are not working?

Please let us know, Ken

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Wednesday, July 18th, 2018 AT 5:57 PM

LEEBK

MEMBER
2 POSTS

I have no heat or cold air. The fan works and is passing air through the vents, but the air will not change temperature.

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Wednesday, July 18th, 2018 AT 6:45 PM

KEN L

MASTER CERTIFIED MECHANIC
48,363 POSTS

This system is vacuum operated. Here are the diagrams to show you how it works it sounds like you have a leak which is not holding vacuum and not moving the doors. Also, check under the hood to make sure the vacuum feed line is intact.

Check out the diagrams (below). Please let us know what you find.

Cheers, Ken

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