Topic: wiring stuff
in Forum: C3 Electrical
Not sure about the wiper motor, but the horn is a self grounding unit. Kind of like the temp sensor in the engine block.

just checking my manual. Do you have the anti theft alarm fitted? If so the wiper switch ground connector doesn't go directly to the ground terminal mounted on the firewall above the wiper motor. You should find a multi pin (3) connector that goes into a loom to the passenger side of the ground connector. This multi pin plug has to be plugged into the ground terminal and then your wiper switch ground connector goes into the multi pin. It would be a lot easie to explain if you had the pic.
As far as the horns go, mine is a '71 and has a horn relay which also operates the horns if you leave the key in the ign and open a door (that part of mine is disconnected cause its a PITA). maybe you have a dud relay? It looks like they both operate off the same fuse too.