1973 240Z Horn signal wiring/relay location

[hotsho111]

Hey, next up on the electrical list is the horn and I've hit a bit of a wall.

If I push the horn I get no noise and no noticeable relay sound. First thing I did was check and swap the fuse and no difference. My column does have the brass arm contacting the steering wheel and I do measure 12V on the red wire connecting to it. I tried measuring the voltage at the horns alone and didn't get any voltage but I'll try and confirm when I can get a friend to help

I also confirmed that when pushing the horn button that the horn switch does get grounded.

To me it seems like an issue at the relay which I want to check next. Looking at the the FSM it says the horn relay should be in the right dash side panel bracket, which I assume is the set below. I don't have much access to that side of the car, but if this is the right area, which of these switches is the horn relay? I think the bottom one is for the wipers.

The left is the front of the car and you can see the closed passenger side door card on the right

Thanks!

Edited June 4, 2022 by hotsho111

[SteveJ]

Look at the junction between the engine harness and the dash harness in the passenger footwell. On the engine harness side, you should see 3 wires with individual terminals going to the horn relay. Those three wires should be green, green/red, and green/black. I'll see if I can snap a picture for you.

[SteveJ]

It's at the top of the relay bracket.

[SteveJ]

I should also add that if your horn relay is bad, don't expect to find a new 240Z horn relay. HOWEVER, horn relays tend to be pretty generic, and I believe this one would work, too: https://www.rockauto.com/en/moreinfo.php?pk=98819

[hotsho111]

Perfect, thanks. 

[hotsho111]

Circling back as I've finally had a chance to look at this. I can confirm the horn relay works. If I remove the ground (GB wire connected to the S terminal on the relay) and directly ground it the horn works. I also independently tested the relay and it worked as well

So the problem appears to be the ground path isn't being completed. There is continuity from the GB wire at the relay to the horn switch (I checked the black wire on the front and the flexible brass arm on the back).

I don't remember how I tested the column originally but I can confirm it *doesn't* have ground. If I ground the steering column (just clipping a ground wire to the ignition switch from the battery) and hit the horn it works as expected.

Does anyone know how/where the column is grounded? Is it just by being bolted to the frame or is there an actual ground wire that should be connected somewhere? I would assume its the former and so maybe there's some paint or corrosion preventing that

Edited July 17, 2022 by hotsho111

[SteveJ]

Do you have any loose wires around the steering column? (Aside from the key in switch buzzer)

[hotsho111]

I took a look and don't see any loose wires. That was mostly looking at the column itself. I didn't get way into the footwell to look under the dash 

[hotsho111]

For the column grounding, is it generally grounded via just being bolted to the body or is there supposed to be an actual dedicated ground wire?

An easy solution would be to run a ground wire from the ignition or turn signal/light stalk to the metal dash bracket which is grounded.

Something else I noticed is there's a slight spark when the column is grounded and I press the horn plates together. That makes some sense since the red/black wire has 12v that touches the back of the steering wheel, but I would have thought that's just completing a ground circuit and there wouldn't be a spark. Any idea what's going on there? (I'm mostly just curious and definitely not an electrical expert so it just seemed a little unexpected) <- Thinking about it more, that makes sense. I figured I'd leave the info there if it helps anyone else though

Edited July 18, 2022 by hotsho111

[SteveJ]

An easy way to see if the steering column is grounded is to check continuity from the shaft where the steering wheel mounts and the body.

[hotsho111]

Ya, I checked that and there isn't continuity

I'm just not sure how the column is supposed to be grounded

[cgsheen1]

The steering column is grounded to the frame by it's mounting bolts. There isn't a specific ground wire connected to it. There is a large ground wire at the steering column to provide the grounds needed by the switches on the column but it's not directly attached to the column itself. Is your frame ground intact?