Good afternoon everyone, would like to get some help in getting my horn to work. I have an aftermarket momo hub and horn button. I have tested the turn signal switch part that touches the back of the hub and it shows 12V. I have the oem relay and an aftermarket one. I have tested both with a powersupply and both click with 12V. The Green Red wire that comes from the fuse panel shows 12V. The Green Black wire that comes from the switch doesn't show anything. The Green wire that goes to the horn doesn't show anything either. I saw that someone else ran into a similar problem, so I ran a ground from the steering rack mount holes to vent opener which seems to be part of the chassis. Am I suppose see 12V on the Green Black wire also? Are there any other tests I can do?

Edited January 3Jan 3 by Cheetoh

When was the last time you heard your horns work?

The way the circuit works is that the GR wire comes from the fuse to the horn relay. The GB wire goes to the steering column to the copper tab on the turn signal switch. When you press the horn button, the GB wire is grounded. That should complete the circuit for the coil on the horn relay. At that point the GR wire and G wire are connected, completing the circuit out to the horns.

To test the relay, take the GB wire off the relay and use a clip lead to ground the S terminal on the relay. (See below.) Ideally, you should hear the horns. Hopefully you at least hear the relay click.

With 12VDC+ on the B terminal and the S terminal grounded, you should have 12VDC+ to ground on the H terminal.

When I was waking up my 73 from 11 years of slumber, I tested my horns. They didn't work. I tracked the problem down to corrosion on the horns where the green wire connects to them.

Thanks, I was able to test that and found out my horn was bad. I bought an aftermarket one and the horn works using that method. Now I need to find out why the Green Black wire is not sending the ground signal. Any ideas on how to test that side?

Edited January 2Jan 2 by Cheetoh

Okay got some progress, I can now verify that the problem is at the horn button/ hub side. When I ground the wire coming from the hub the horn sounds. The hub comes with a metal ring where the horn wire can attach but nothing happens when I press the horn.

Did you get instructions with the hub about connecting the horn? I haven't touched a Momo hub in years, so I cannot recall how it was set up on the horn button.

Are you sure the tab on the turn switch is making contact with the horn ring on the back of the steering wheel?

Is the steering wheel grounded such that when you press the horn button, it completes the path to ground on the horn ring?

Yeah, its making contact. I am going to remove the hub and inspect it. I want to make sure there isn't a protective film over the back of the hub. When I tested that little arm, it was showing 12 volts so it should be grounding the hub. I have owned this Z for over a decade and the horns never worked, it had other wiring issues so I never messed with it. Sadly back then I didn't know alot about cars so most of the work was done by a shop. I have been looking at videos and most setups are using a modern horn that has two connections on the back. There are two connections, one from the hub and the other from the ring adapter that connect. Mine only has 1 connection on the horn button.

I removed the hub, cleaned the contacts and the back of the hub. When I ground the wire coming out of the hub the horn goes off. I thought the Green Black wire was the one grounding the hub? I don't know how I would go about finding another ground to add to make it work. Is the steering rod supposed to be grounded?

I want to thank everyone for the help, I was able to fix it. My rack wasn't completely grounded. Special thanks to Hotsho111 who suggested checking out the coupler for ground. I grounded that and then kept working my way up to shaft to see where I could no longer fix a ground. I tried drilling a hole for a tap but the metal was too soft and just kept crumbling. I ended up just running a self tapper to the ground near the vent pull.