I am a defeated man. My 1987 190D Turbo climate control has defeated me

I have now replaced the swichover valve ($$) behind the glovebox and the pushbutton climate control unit ($$$) and I still have problems.

Current symtoms - The blower comes on sometimes, sometimes the fan switch works and sometimes not, same when you push the defrost button, sometimes it works, sometimes not, and sometimes the defrost button will work for about a half second and then cut out. When this happens, the fan switch will no longer work either. Sometimes turning off the car and restarting will make it work for another half second.

Based on reviewing other posts, I tried jiggling the ignition key, but that seems to have no effect on the operation of the fan. I also tried replacing the fuse, in case it had a crack in it or something.

Any ideas?
Help.
Thanks
George