[T3] Invasion prep

[Jim Adney]

I want to clarify some details about the ground side of the horn circuit. It has 
two halves: the "hot" side and the grounded side. The two halves are 
separated by the horn siwtch in the steering wheel hub.

The description below is for '70 and earlier. Everything changed in '71.

The "hot" side of the horn ground circuit consists of the brown wire leading 
from the cold side of the horn to the steering shaft. I'm not clear on where 
this path runs. In early cars, there is a ball bearing at the top of the steering 
column that is insulated from the rest of the column by sitting in a plastic 
cup. Somehow the brown wire is connected to the outer race of that bearing, 
so contact to the steering shaft is made thru the bearing. Note that this 
makes the WHOLE steering shaft, including the steering wheel hub, "hot." 
This MAY be how all cars prior to '71 are wired.

I've heard of the plastic cup that insulates the bearing breaking down. That 
could be a problem here, but usually if the cup is broken, the horn would 
sound all the time, but maybe there's something in there making poor 
contact.

To sound the horn, the horn ring is connected to a wire that runs down inside 
the steering shaft (which is "hot") and jumps acorss the insulating flex 
coupling.to the steering gearbox input shaft. The jumper from the steering 
gearbox to the pan horns complete the path to ground.

I note that in Max's picture of his steering wheel hub, the wire running into 
the steering shaft is missing the black rubber grommet/plug that keeps it 
from rubbing. I don't normally think of that as a problem, but it could be in 
this case. I may have one of those, if needed.

So, when the horn is not sounding, the entire steering shaft and the steering 
wheel hub are "hot." Grounding anything there should cause the horn to 
sound. The horn ring is part of the cold side of this circuit, so depressing it 
makes contact between the grounded "cold" side and the floating "hot" side, 
causing the horn to sound.

Okay, now I've checked the parts list and I need to add a few more details.

Up thru '67 things are as described above. The steering shaft ball bearing 
and insulator appear to be sold as a single combined assembly. It looks like 
it has a connection for a wire, presumably the brown wire for the "hot" side of 
the horn ground circuit.   

>From '68 (when the collapsable steering shaft started) thru '70, the ball 
bearing is sold separately and the insulator is in L & R halves. One of those 
halves appears to have a connection for a wire, presumably the brown wire 
for the "hot" side of the horn ground circuit. There is a "contact ring" that 
plays some role here, but I'm not sure how it fits in this circuit; it may carry 
current from the outer bearing race to the shaft, to keep horn current from 
running thru the contact points between the balls and the races. I suspect 
that the horn ground circuit remains pretty much unchanged.

In '71, everything changed.

Max, I hope some of this helps. Let us know what you find.

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