noctum

1989 560 sel-gas 171.600 miles.
I am new to this forum, glad to find it.

This is driving me nuts.
When driving over 40mph, even when "0" is selected I get warm air coming out of my vents.
The air works whenever it wants to? and when it does I also get hot air on the window and those small vents by the doors and foot vents-at the same time?.

I get cold air in the middle vents across all 4.

I have been reading posts and I do not know what to start with?

monovalve?
fuse?
Climate control unit replacement?-$$

Thanks in advance

Jer

When the climate control is shut off, the fresh air damper is supposed to shut. If this is not happening the vacuum element might be leaking. Big job to replace...

If the heat operates concurrently, the climate control unit might be bad. You can get rebuilt units online at www.thepartsbin.com.

noctum

Thanks for the suggestions.

If the climate control unit does not fix the problem then I need to do the vacuum element.

Is there a was to diagnose which one is the problem?

Thanks

braverichard

While we are at climate control issues, I have two questions to ask about my own W126 sedan.

1) When set to the minimum temperature, cool but not cold air blows? What could be the cause? Needs charging? More coolant? Could the coolant be leaking? Any help would be appreciated.

2) When set to heating, air comes out of the vents by the doors as well as from the vent in the rear seat area, but very little heat comes out of the big vents in the middle. These vents blow out air well when set to cool but not when set to heat. Any idea of what's going on here? Even the local mechanic told me he has to look at the car before he can answer my question.

Thanks for all the help.

Jer

noctum: See if you can find a salvage control unit and swap it with your current one. You can test the vacuum element by hooking up a vacuum pump to the vacuum hose at the switchover-valve block. It is located behind the glove box, therefore you will have to remove the glove box.

braverichard: If the air is not frigid (it should be ice cold), the refrigeration system is low on freon, the compressor has failed, or the Klima control unit (protection) is faulty.

Warm air does not blow from the center vents. This is to divert as much air as possible to the windshield for purposes of defogging. Safety first!

braverichard

Thank you so much for your quick response. Now I have an idea of what's happening.

noctum

Jer, thanks so much for your assistance.

Is there anything I need to know about
replacing the Climate Control Unit?

Does the wooden panel lift off/slide?

Do I need to remove the radio?

Thanks........

Jer

You do not have to remove the radio. There are two Phillips-head screws under the wood panel (on the lip above the radio). Remove them and slide the console downward and out. Be careful not to break the tabs!

Disconnect the battery before you remove the pushbutton unit.

braverichard

I just got my system professionally converted to the new R134a A/C system for $225. The A/C now works perfectly. I just installed an in-dash CD/MP3 player and a trunk mounted 10 CD/MP3 changer in the car. All that's left is to install a remote keyless entry system, get the windows tinted, replace that steering wheel with a smaller one from a different benz and then put 18" rims on that benz and it will be all set as my new pimp-mobile!!