I finally got it....

One of the switch electrical harness was entangle in the shaft of the AC knob...

I had to remove the 4 switches, lift the plate up about 1/2 inch dis-entangle the harness then pull out.

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1980 300TD(euro non turbo): Eng: 617.912 /Tran:722.118
1985 300SD: Eng: 617.951/Tran: 722.416