1973 911 steering column grounds

[Sparky73]

I am working on my restoration of my 1973 911 and have more wiring questions. This has been a real roadblock for me.

I am trying to figure out the how to get my horn to work. I have an aftermarket momo Porsche steering wheel.

There are two brown/white wires
1. One wire comes from the blinker switch and connects to the tone ring that sits behind the steering wheel
2. There is a second brwn/wht wire that comes from the wiper switch.... Where does this connect ?

The wiper switch is working
The blinker switch is working (with some issues)

The second issue is when I test both of these wires for a ground, they are negative, so they are not grounded.

Both wires run back into the main wire harness into the front Frunk

Any thoughts on what I am missing to get the horn to work ?

[Sparky73]

add a picture

[proporsche]

back in the 1980-90`s if we have found lost ground to the steering shaft we did this.On the picture.
I took feeler gauge, cut short piece drilled hole in one end and attached it over the steering shaft to gain a ground.
Ivan

[wazzz]

Originally Posted by Sparky73

I am working on my restoration of my 1973 911 and have more wiring questions. This has been a real roadblock for me.

I am trying to figure out the how to get my horn to work. I have an aftermarket momo Porsche steering wheel.

There are two brown/white wires
1. One wire comes from the blinker switch and connects to the tone ring that sits behind the steering wheel
2. There is a second brwn/wht wire that comes from the wiper switch.... Where does this connect ?

The wiper switch is working
The blinker switch is working (with some issues)

The second issue is when I test both of these wires for a ground, they are negative, so they are not grounded.

Both wires run back into the main wire harness into the front Frunk

Any thoughts on what I am missing to get the horn to work ?

Brown/white is usually not a standard ground, but a switched ground. It will show a ground only when the relative switch is acted upon. Brown/white from horn button goes to pin 85 of horn relay.

See this schematic for MY73. Once you download the pic you can zoom in and see full details.
https://i.postimg.cc/qvPgVCDp/Planche-07.jpg

[Sparky73]

thanks guys for the information. that makes sense that there is no ground until the switch is acted.

where is the horn relay located ? I assume that is down near the fuse panel towards the front of the car.

Still trying to figure out where the brwn/white wire from the wiper switch gets connected.

[blucille]

there is a brown/white that goes nowhere, I know this because I just put my 72 back together after paint, and it was source of concern until I checked with a few friends and read some old posts.

[Sparky73]

A little surprised that the second brown/white goes nowhere. Why would it be like that ? Appreciate that might true but .....

I still can't get my horn to work and I think it has to be related to the ground wires at the wheel.

Still searching for answers

[blucille]

some references to the brown/white that goes nowhere:

https://forums.pelicanparts.com/porsche-911-technical-forum/994543-1973-t-wiper-switch-wiring.html

https://forums.pelicanparts.com/porsche-911-technical-forum/754879-why-do-i-have-two-horn-wires-steering-column.html

[Sparky73]

thanks for sharing these. I actually have stumbled across both of these already. I have tried leaving the wiper switch connected to the wheel and with it left loose. Unfortunately I still have no horn. I am thinking my grounds are fine but that there is a different problem. It is a brand new wire harness, so maybe something is not right from a pin standpoint.

[blucille]

as Proporsche / Ivan mentioned above, I had a car that I couldn't get the horn to work, turns out it had a rubbery steering shaft bushing installed instead of the (same as the 928 version) metal version, so the steering shaft was not acting as a ground.

In other words, a quick test would be to put a temporary ground wire on the steering shaft itself and determine if that fixes your horn problem.

[Sparky73]

great tip, thank you. I will try that tonight.

[Duc Hunter]

Just had my 1975 apart. I replaced the steering shaft bearing. I took out the rubbery one and installed the billet aluminum one from Rebel Racing. The horn worked before so I am not sure that is the issue. I think the 2 wires to the horn button come from the horn relay, but I don't have my wiring diagrams in front of me to check.