1982 300D: Any time "O" is selected on the climate control or the key is turned off, the only way the fan will come back on is by selecting Defrost. After that, the fan works normall in all modes until you hit "O" or key-off.

Also, the (new) A/C compressor was working well but has now stopped coming on at all. Checked the relay, both switches on the receiver/dryer, etc. - all circuitry under the hood seems intact and it will only come on when I jump the 87/30 terminals of the relay.

I've swapped out the climate amp and "button box" (control head) to no avail.

Any help is appreciated!

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'82 300CD
"Pearl", the very first turbo diesel 123 coupe
Totaled 11/23/18, rebuild in progress.
'85 300TD, "Artemis".
'78 300D euro, "Ol' Red", mostly retired.
'85 300D, "Gandalf".

So, just to cover bases. You are aware that there is a temp switch which won’t let the blower come on until the engine reaches a minimum temp (I think 40*c???). The defrost button will over ride this.

Nope, never heard of that. Where's this switch located?

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'82 300CD
"Pearl", the very first turbo diesel 123 coupe
Totaled 11/23/18, rebuild in progress.
'85 300TD, "Artemis".
'78 300D euro, "Ol' Red", mostly retired.
'85 300D, "Gandalf".

That's not right ~ every Klima II equipped W123 I've had will run the fan with the engine off or cold , it just takes a few moments for the control to begin it turning after you turn the key on .

Most often the fan motor's brushes are worn out, easy to replace, you'll need a soldering iron .

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-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better