HELP! W126 Climate Control Schematic Please.
 

I have NO blower operation in any mode on my 82 300SD (including in DEFROST)... I tried a different CCU, but it has the same problem. After that, I checked something I should have checked first.....

I have NO 12 VDC on either of the connectors that connect to the CCU (the 2 twelve pin connectors, one each, left and right side of the CCU).

I know my blower motor is good, she works well when hot wired..... The fuse for the blower motor (#11) is good as well.

How does power get from the fuse to the fan? I know it goes thru th CCU and the blower motor control unit, but I'm not sure where to start to isolate it.

I can read schematics well, but I don't have any.... does anyone have a wiring diagram they could post?

Thanks

Phil

I have one that I can look at, but I have no means of posting it.

The CCU is powered from fuse 11 through connector C2, terminal 12. The blower speed control module is also powered from fuse 11, terminal 12.

I checked fuse 11, it is good and it is also making a good connection in the holder.

Where is terminal 12? Is there a terminal board box somewhere?

Which connector and pin does power go to for the CCU. I may try to "hand over hand" it back to the fuse box.

Thanks TangoFox!

Phil

The schematic I have shows F11 provides power to the Electronic Unit for Blower Speed Control. This unit interconnects the Blower Motor, Blower Resistors, Pushbutton Control Assembly & Temp. Control.

I noted that you mentioned no 12VDC to the Pushbutton Control. F10 provides power to the Pushbutton Control at pin 12 of connector #2 (black/red wire). This same fuse, powers the Temp. Controller.

From your description, I would suspect F10. However, if you are still having problems, I could possibly scan the schematic I have and send it as an attachement. I'm not sure how good the detail will be. MBUSA has the manual available for download but you will need DSL or better.

What year does your schematic appy to? Mine is for the 1982 300SD. It shows that the CCU/Blower Module is powered through F11. Temp controller through F10.

On the CCU, connector 1. Should be a Red/Yellow wire that is hot with the key switch in "Run."

I hope you can read these they are pretty fuzzy.

It is for an 82 300SD W126. (paper copy)
It shows F10 powers the Pushbutton Unit and the Temp Controller.
and shows F11 powers the Blower Speed Controller.

That's interesting. Mine is a paper "foldout" from the 1982 Electrical Troubleshooting Manual. 1982 Model 126.120.

Upon further inspection, there is another schematic in the book which shows the CCU being powered from F10. Go figure.

Thanks to EVERYONE!

I ended up downloading a service manual, and fixed it in 10 minutes!!

SD Blue - you hit the nail, it was fuse 10 power to the CCU. The blower fuse #11 was good but I had no juice to the CCU relay board. It was the fuse holder itself, not the fuse. I heard the blower come on while I was under the hood and fooling with it (got a little spark as well)........... I cleaned all the contacts and all seems well now.

The fuse box cover isn't very specific on what feeds who, so I was a little lost..... once I had a proper schematic, it was no trouble.

I don't know the copyright rules, but I now have a full 126 service manual. If anyone else needs something, let me know, we'll figure out how to get the info to you.

Again, thanks everyone....

Phil

Check your local library
 

I was at the library today, and was surprised to see Chilton manuals, for all kinds of cars "Import cars from 1989-1993" for example, not books on just a specific car. But when you open that up, they have all kinds of cars listed, with specs and exploded views.

jeff 1991 300d

Replacing the original aluminum fuses with brass/copper fuses will eliminate much of the fuse box corrosion and associated problems. Less than $10 on Ebay.