The good news is that the horns work fine but only via a bypass button that the previous owner installed. I've read that this is not an uncommon remedy. I'm trying to trace down the break in the original circuit starting with the contacts that I've un-covered in the steering wheel. Were does the wire exit the steering column and where does it go from there. The fuse is not blown and I understand there is no horn relay. Anybody done this before? TD

 

if you ground the horn switch at the steering wheel it doesn't go off?

the circuit goes like this...

red wire from battery to positive terminal to ignition switch pin 30
black wire from ignition switch pin 'X' (on in accessory and run) to fuse 15 and 16
yellow wires from fuse 15 to pin 15 of the wiper relay to pin 35a of the wiper control stalk to left A post big block connector B pin 4 to horn + terminals
blue-black wires from horn - terminals to connector B pin 17 to steering column 'ring'.
black wire from ring slider to horn buttons, which go to ground.

so... when the car is switched to II (on), is there power at the yellow wire to the horns?

if you ground that ring switch, does the horn honk?

 

Thanks. This is just what I need to know. I'll run these tests tomorrow and get back to you. TD

 

oh, I used the schematics for a 1992 740/940 as I had them open. different years are /probably/ the same.

 

The whole circuit checks out down to & including the horn switches themselves except the grounding wire within the steering wheel. When I run that to ground everything is perfect. I'm sensing the airbag holder has to come of to trace the wire & that sounds a little foreboding! Is there any danger involved in doing that? Seems like there are only two screws securing it from the back. TD

 

disconnect battery ground cable, wait an hour for any residual capacitance in the trigger circuit to discharge, then it should be totally safe.

 

Make sure you lock the clock spring into place, otherwise it will unwind and it is tricky to rewind it. Use the lock screw provided (should be labeled) if the steering wheel has to come off when you are working on this project.

 

Can the orangish wire to the air bag case just be unplugged? I learned the reason why this horn has been rewired. One of the torx screws holding it on was very tight & almost stripped out so whoever had tried to remove it long ago just gave up. Thanks to the experience of removing thousands of stripped screws from aircraft in the USAF in the '70s ... it's out. Only have to find the break in the grounding wire now. TD