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Old 11-26-2011, 09:42 PM
Marky Maypo Marky Maypo is offline
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Join Date: Aug 2011
Location: Live in Stuart, FL Work in Dover, DE
Posts: 2
Thanks for the detailed pics. I also visted your blog site great information a great help for 10 thump newby! I have '82 300SD.

Originally Posted by patbob View Post
and on...

Attachment 48576
remove bottom cover. Three tabs (yellow circles) and then it hinges off.

Attachment 48577
With the front finally off, the fan switch unit can be removed -- squeeze tabs together gently jsut until they clear and the unit can be removed. It unplugs from the side of the ACC like the temp wheel did.

Attachment 48578
Phew. Now the cover hinges up and off from the guts. The black plastic side pieces that fit over the pins slide off over the pins. Leaving you with...

Attachment 48579
..this. Well, not exactly this, I forgot to take pictures of the inside of the w123 ACC unit when I got this far, so here's a picture of my w126 practice unit. The w123 ACC has only four relays and the circuit traces are different, but otherwise it looks the same. In this picture you can see the four circuit boards that make up the unit -- the main board on the bottom, the daughter board above it, sandwiching the button switches, and the two side wing boards.

Attachment 48580
And here's what a cracked solder joint looks like. All of these are cracked. I even slipped a piece of paper in between one to demonstrate. For me, these were visible with only the bottom removed, but others have reported that the button switch solder joints on the daugher board sometimes break, and you can't get to them without a full disassembly.

hope this helps
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