73 anti theft horn

I tested the horn on the font horn with the wires and hit the horn button and it works. I fixed all the door and hood switches and the key switch. When I turn the alarm on and open the door the horn almost goes on but sort of just clicks and lightly chirps. I checked the relay in the rear compartment above the jack and even replaced it with a new one. I double checked the yellow wire on the horn bracket and made sure it made a good ground by removing the painted surfaces. I don't want to give up so I hope you guys can help me out again. Thanks

Chances are the flasher is bad. Have you replaced it yet? It is in the rear compartment, close to the alarm relay. If you replace it, don't use a "heavy duty" flasher...just a regular turn sig flasher is best. 

Thanks Joel, I replaced the flasher and there is no change. Maybe I need a stronger battery.

SO, new pin switches, relay, flasher, and you know the horn is capable of tooting properly. At this point, I would suggest using a volt meter AT the horn connection, and verifying if you do or do NOT have full battery voltage there, with the alarm triggered. With just the volt meter attached, you may not see it pulse on-off as it would with the horn connected, but you should see battery voltage at the connection. You should also have full battery voltage on one of the flasher terminals with the alarm triggered. This all assumes, of course, that you have battery voltage at the relay. So...you need to start checking voltages at the various components & connectors. I think this will wind up being a voltage issue, and not a ground issue, since the relay does appear to be tripping when the alarm is triggered. I do have, somewhere, the wiring/system diagram for the '73-'74 alarms...if I can find it.

Thanks Joel. That is good info. I will check everything out and let you know the results. Thanks again