The climate control on my 300SD is completely nonfunctional.
No fan, heat, air - no nothin'
I've checked the fuses in the fuse box and everything is OK.
I've searched previous posts - and while there seems nothing that addresses my specific problem - there have been
suggestions that the ignition switch may be at fault.
I've inserted the key - and as suggested "jiggled" the key at different radial locations of the keypath - and still nothin' !

Can anybody offer any assistance in troublshooting this problem ?

Thank you

You failed to mention whether you have the 1980 and older system or the 1981 and newer system.

__________________
Auto Zentral Ltd.

Sorry for the deletion!

It's an 84.

Climate control problems are no fun

Do you understand how the system works.
There are two systems electrical and vacuum

It sounds like you have an electrical problem most likely with the control unit. I replaced mine this summer as I fried it in trying to investigate my vacuum leak (disconnect the battery).

THe vacuum system can be checked using a vacuum checking device (hand held pump) that you can buy at any parts store.

Ok Back to theory. The climate control unit controls the opening of switchover valves which the supply vacuum to five vacuum circuits in your cars interior. (Vacuum elements open up the vents) The climate control also controls the fan blower and the monovalve which controls the temp. The blower fuse on your car should be blue and 25 amps carefully check that fuse and to be on the safe side replace it. I do not think that there is any other protection for the climate control unit.

There are many links in the forum to diagnosis the vacuum lines and problems. Check the green source line under the hood as it enters the fire wall.

THose control units are expensive about 200 bucks rebuilt.

good luck

bob

Glennet,

The best way to diagnose the system you have is with a DVOM at the connector to the ECU (electronic control unit),but I couldn't even begin to guide you using the internet.The system is fairly complex.You might have something as simple as worn blower brushes. Drop the passenger under dash panel, and smack the blower with a small hammer.Good luck.

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Auto Zentral Ltd.

If your AC still isn't working, don't jest check the fuses, replace the fuses. I had a similar problem and the fuse looked okay. Everything worked fine after I replaced the fuse as advised by this forum.

Regards,
Sixto
91 300SE