Officially confused by Momo horn wiring

[Tremelune]

I have a 1970 911T that's had a Momo steering wheel since I bought it. The horn has never worked (though it does when I jump the wires). I've taken the wheel off, got a look inside, and purchased a plunger that rides along the metal contact ring. I just don't see how the pieces can connect and work.

If I'm not mistaken, the wheel itself is grounded by the column, which is itself grounded to the chassis as well as a dedicated wire (the brown wire attached to the steering column on the right). This would mean that the brown/white wire dangling on the left is hot and connects to the contact ring.

This is where I get lost. The plunger rides along the hot, and is connected to the horn button. The wheel is grounded, and there is a switch in the button in the wheel...but the button has nothing to connect the hot to. Like, if I push the horn button, it connects hot to nothing. How do I ground the horn button without having a wire twisting around in there?

Am I crazy? My best guess is that I have the wrong button for the wheel, and I need one that has a sort of ground wire that sticks out of the side and runs along the inside of the wheel (which is grounded)...Any insight would be appreciated.

I have half a mind to just...connect a ground wire to the wheel somehow. Either drill and tap for a screw or just...wrap a bunch of wire around a spoke!

[930cabman]

Unless you really love the MOMO (I don't care for them), go back to a stock setup

[Tremelune]

I'd love a factory wooden one, but while I contemplate spending $8,000 on a 60-year-old used steering wheel, I'd like to see if I can get the horn working on this one first.

[HarryD]

The adapter hub in your first picture holds the plunger. This picture is the collapsible one like yours with the outer rubber sleeve removed.



On the base at the top, you see a wire exiting the hub. The Plunger Thingy goes through the hub and contacts the copper ring (in your hand above) which is attached to the steering column. The horn button connected to the wire.

If you have not already, you also need to also have one or both of these parts:



and they get installed like this:



Bushing Part#: 695.347.725.00.
Spring Part#: 914 347 713 00

[Tremelune]

This ain't the right horn button for the wheel—I think the seller just jammed in whatever they had lying around. Every time its inserted it bends the metal grounding ring...I think it's supposed to have this perimeter ground slider:



Anyway. In one of my more comical repairs, I just grounded it to the spoke of the wheel. We'll see how long this works while I wait for proper parts to find their way to me.

[HarryD]

Your horn button looks fine. It similar to the one on my working Momo wheel.

Do you have the plunger contact installed at the base of the Momo Adapter? It is the item circled in this picture. This is what connects the horn button to the contact ring in the steering wheel column. There is a wire on the other side that connects to the button.



Here is the inside of my adapter and the wire for connection to the horn button.



Note that the silver ring in the picture above is between the back side of the steering wheel and the horn button to hold the horn button in place and the wire is attached to the button.

[HarryD]

Also, the loose wire you show in the first picture is attached to the terminal on the brass contact ring.

[Tremelune]

Appreciated, but my issue was grounding the horn button. Your horn button has a springy wire along the perimeter that touches grounded metal on the wheel, and mine does not.

I'm probably just going to run my janky wire until it fails or I get a new wheel!

[HarryD]

Originally Posted by Tremelune

Ah. I understand the issue now.

If the ring on your steering wheel adapter plate has a spade lug, you could run a wire from the spade lug to your ground on the horn button. Or you can sandwich a wire under one of the steering wheel screws between the wheel and the hub.

In a more desperate move, looking at the horn button, is that spring at the perimeter your potential ground contact? If so, if you unclip just the end of it from the button does it to form your ground contact to the shell assembly?

[Tremelune]

Alas, that metal ring is just a spring to keep the prongs under tension once installed. I could rig a few things up, but they wouldn't be much better than what I have.

The real solution is just to get ahold of the right button!

[HarryD]

Do you have the metal ring shown in the lower left of this picture (I can’t tell from your pictures)? If so, all you need to do is make a short jumper.

[Tremelune]

I do—and that would have been the better place to ground—but I figured that out after I had the wheel back on! I might have to take it off again if it's crooked, and that's the route I'll go.

[HarryD]

Originally Posted by Tremelune

I do—and that would have been the better place to ground—but I figured that out after I had the wheel back on! I might have to take it off again if it's crooked, and that's the route I'll go.

If the wheel does not need to be rotated, all you need to do is remove the 6 bolts from the wheel.

FWIW, this is my spare Momo Horn Button. Yours is missing the ground spring.





If you need to get a button, we can make a deal.