Horn on my 72 just quit working.

[BillGrissom]

Your 72 horn wiring is totally different than my earlier Mopars (64, 65, 69). Good work 67Dart273 on finding the schematic mistakes. I also traced it thru the T terminal to the starter relay and said "WTF?". Somebody mixed up the "DK GREEN RED" and "DK GREEN RED TR" wires. Anyway, sounds like the problem is in the wiring or switch in the steering column.

If like my cars, all the horn button does is ground the black wire. It could be in the button itself or in the wiring/connector to the steering column. First check at the connector (easy). If OK there, you will need to pull the steering wheel. There is a good tutorial on your car w/ photos posted on FABO. Needed, since your in-column key switch with steering lock is pretty complicated.

Finally, why did Chrysler integrate the horn and buzzer? Must be some dubious feature like "don't sound buzzer while horn is blowing".

 

[Paladin06]

Any idea where I might get a slip ring/ brush?

Sure sounds like it. Backtrack to the column connector and back probe it there. If you get it to blow right there at the connector it just about has to be either the switch or the slip ring/ brush.

 

[Paladin06]

I'd really appreciate a link to that DYI.

Happy New Year!

Your 72 horn wiring is totally different than my earlier Mopars (64, 65, 69). Good work 67Dart273 on finding the schematic mistakes. I also traced it thru the T terminal to the starter relay and said "WTF?". Somebody mixed up the "DK GREEN RED" and "DK GREEN RED TR" wires. Anyway, sounds like the problem is in the wiring or switch in the steering column.

If like my cars, all the horn button does is ground the black wire. It could be in the button itself or in the wiring/connector to the steering column. First check at the connector (easy). If OK there, you will need to pull the steering wheel. There is a good tutorial on your car w/ photos posted on FABO. Needed, since your in-column key switch with steering lock is pretty complicated.

Finally, why did Chrysler integrate the horn and buzzer? Must be some dubious feature like "don't sound buzzer while horn is blowing".

 

[67Dart273]

This is probably it, but it deals more with the ignition switch:

http://www.forabodiesonly.com/mopar/showthread.php?p=1706113

Here download yourself a free 72 factory shop manual:

[ame]http://www.abodyjoe.com/pictures/Misc.%20car%20info/1972%20Plymouth%20Chassis%20Serv%20Man.pdf[/ame]

I'll admit the factory manual is not that detailed, IE removing the horn ring/ pad, etc.

 

[BillGrissom]

Above is the post I meant. The "slip ring / brush" refers to the spring-loaded copper "horn contact roller" on the turn signal switch (white plastic in photos) which rolls on a copper ring on the underside of your steering wheel. If you ground that roller, the horn should sound. If not, the problem is in the wiring down the colum. Again, before removing the steering wheel, try grounding the black wire in the bottom column connector (body side). If that doesn't sound the horn, the problem is not in the steering column.

Finally, I just remembered a problem when my horn stopped working in my 65 Newport. The horn button was good and when I shorted the roller to ground, the horn worked. The problem was that the ground path was thru the steering rod and C-bodies have a rubber isolator in the engine bay so those elegant drivers aren't bothered by nasty road feel. The jumper wire across the isolator had broken. Shouldn't be a problem in A-bodies since should be metal-metal contact thru the steering coupler. The rod does float at the top end since the bearing is shrouded in rubber, at least in my 1965 Dart.

 

[Paladin06]

Well the "slip ring / brush" which refers to the spring-loaded copper "horn contact roller" on the turn signal switch (white plastic in photos) which rolls on a copper ring on the underside of your steering wheel was stuck down. A slight tap freed it. Wow!!! Damn car tore apart for that tiny stuck device.

Thanks everyone for your help and this learning experience.

Happy New Year!!