[T3] Horn 70 Fastback

[Jim Adney]

On 24 Aug 2015 at 8:17, Dennis Stiefel wrote:

> We are getting closer to have the 70 Fastback ready for auction. Right
> now we are working on getting the horn working.  Since it's a 70 most
> of what I learned on my 72 in this area is out the window. The horn
> it's self-works is getting 12V+ at the horn + terminal.  When you
> ground the horn wire at the group of wires coming out of the steering
> column underneath the horn will sound off. But when you ground the wire
> coming out the center of the column under the horn ring nothing. What
> will we have to do to get to this wire and circuit going inside this
> since this seems where our problem is?

As you said, the horn circuit all changed in '71, and the Bentley is 
not clear on any of this.

For '70 and earlier, the wire coming up the center of the steering 
shaft is a ground wire (note that it is brown.) Check it with an 
Ohmmeter to make sure it leads to ground. If it does not, look under 
the car, where the steering shaft connects to the flex disk. That 
brown wire should come out of the collision crush sleeve, around the 
flex disk and connect under one of the nuts that ground it to the 
steering gearbox. Then there should be a ground jumper between the 
top of the gearbox to one of the clamp bolts for the front axle beam. 
That completes the circuit to ground.

The steering shaft and steering wheel hub should be "hot", meaning 
that the - side of the horn is connected to it. Grounding the 
steering shaft should set off the horn. If it doesn't, there's a 
problem with the connection between that wire and the steering shaft. 
That connection is done thru the steering column bearing, which sits 
in an insulating plastic bushing. I think that wire connects to a 
copper piece that wraps around the outside of the bearing's outer 
race.

So the - side of the horn is normally hot and the horn goes off when 
that side gets grounded.

That circuit goes like this: the wire from the - side of the horn to 
the steering column and the outer race of the bearing. Outer race 
thru the bearing to the steering shaft. Steering shaft to steering 
wheel hub.

The horn sounds when the horn ring, which is grounded by the brown 
center wire, is pressed against the steering wheel hub.

Yes, it all seems more complicated than it needs to be, but in the 
long run I think it's less complicated and easier to keep running 
than the later system.

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Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
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