Hi there,

I'm trying to diagnose the cause of multiple power windows failing on my 79 300sd. Have tested the driver-side window motor (it was fine) and the driver-side console switch unit (also fine).

I'd like to take a look at the relay (or relays) for the power windows but I'm having trouble finding it.

Searched the online wiring diagram but diagram 8 (which covers the power windows) seems to be missing.

According to my Haynes manual (covering other diesel models of the era but not specifically the w116 300sd [which seems to have been produced only for the American market]) there are (in at least one other model) two relays for the power window motors (one for each side?). On the other hand, the wiring diagrams for the US model 300cd and 300td indicate that these models have only one power window relay so my guess is that the 300sd does as well.

Thanks for any insights you might have.

Best regards,

Linus