1995 E300D M606 auto

I have no signal (ground or 12v) at the Klima from either the WOT switch or the PBU in any scenario. (I believe from a post from Sixto last year that I should have 12v from the WOT switch normally and a ground signal from the PBU when calling for a/c.) It seems a coincidence that there is nothing from either so I was wondering if there is a link between them other than at the Klima?

I have bridged 12v to compressor at Klima to do these tests and the system works.

can anyone advise , Sixto?

thanks
Keith