The vent fan on my 82 300TD does not spin regardless of speed setting. I have checked the fuses and even pulled the fan motor plug and applied 12V power and it spins right up.

Are there other relays in question other than the pushbutton dash control?

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1974 240D 3.0L 4(M) - 250K -OM617.910 + 300D FW + Rajay turbo power!
1977 6.9 3(A) - 84k

Has anyone had fan speed issues with their climate controls?

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1974 240D 3.0L 4(M) - 250K -OM617.910 + 300D FW + Rajay turbo power!
1977 6.9 3(A) - 84k

I'm working through a similar issue with my W116 300SD. It actually ended up having a bad blower (actually very easy to replace on this chassis, don't know about the W123), but I only get blower activity on the Defrost setting (which I think overrides the servo control of the blower speeds) and I don't get anything but warm air so I'm pretty sure it is servo related. If you can't get your blower to come on at all, I'm thinking you may have a bad pushbutton control, as I have seen the button contacts go bad on a W123 before.

Fortunately everything is working on the W116!

I swapped the unit with a working one and it seems to be working fine. I guess the pushbutton control is just not working.

I disassembled the fan speed control and the switches do not appear to be corroded.

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1974 240D 3.0L 4(M) - 250K -OM617.910 + 300D FW + Rajay turbo power!
1977 6.9 3(A) - 84k

Automatic CCU? These things fail regularly.

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83 SD

84 CD