Climate Controll '78 300D

[mark300d]

Hi all,
I have a problem with my climate control. The green line that goes to the climate control looses vacuum really bad when the climate control switch is in the off position. (This depletes my vacuum and kills my door locks!) Have any of you had experience with this kind of problem? Any suggestions?
I think the switch on the climate control unit is bad, but I do not have a schematic for the unit and do not want to open it up without knowing what I am getting into.

Thanks in advance for any and all info.

Mark.

[P.E.Haiges]

You might have a vacuum line that comes out of the climate control valve that is pulled off its connection or a vacuum servo with a leaking diaphragm.

Block the outputs of the control valve one at a time and see which one corrects the problem. Then you know where to start to look for the leak. Sometimes you can find the leak by sucking on a vacuum line. None should have a continual flow of air when sucking on it.

P E H

[mbdoc]

When you press the O button the fresh air doors are pulled shut. The vacuum elements are likely to be leaking. They are behind the glove box.

[mark300d]

Wow! That is so simple that I will try it tonight after work. I think I might even have a spare actuator somewhere.
I will keep you posted.
Thanks.

Mark.

[P.E.Haiges]

If the rubber in the pneumatic cylinder is not torn but just leaks around the perimeter, you can repair the cylinder by putting a thin coat of JB Weld around the perimeter and replace the rubber onto the perimeter of the cylinder. I repaired mine this way and they work well..