Broken Horn Brush

When I was putting the steering column back in place after re-installing the dash, I made a boo-boo.  The column didn't want to fit back into place.  I thought that it was just tight where the bolts fit, so I gave it a shove.  It went into place all right, but I didn't realize until later that I had broken off the carbon brush that lets the horn button work.

The horn circuit works by the horn button grounding the solenoid on the horn relay.  That energizes the relay and power flows to the air compressor.  Since the horn button is in the middle of the steering column, it can't have a wire running to it since the column rotates.  Instead, there is a brass collar on the column with a spring loaded carbon brush that makes contact with the collar.

As I was checking out each electrical item in the dash, I realized that when I dropped the steering column down, the spring forced the carbon brush out of the holder into where the column fits.  As you can see, the old piece has the carbon broken just beyond the spring end.  Luckily, this part is readily available at an inexpensive price (<$10).  Usually my errors are more costly.

The original spring was soldered to the wire directly.  I couldn't get the new spring tinned, so I decided to make it a little better.  I found that a 6-32 brass screw would fit tightly inside the new spring.  So I drilled a 5/64" hole in the end and cut off a short piece. 

Then I soldered the wire into the hole and screwed the spring on.

Here you can see the whole thing assembled with the arrow pointing to where the carbon brush rides on the collar.

In my PF Coupe, instead of a carbon brush, U-shaped metal brushes are used to contact the brass collar.

I think that the carbon method is a good advancement as long as somebody doesn't do something stupid like I did.

When I got everything back together, the air horn didn't work.  It was drawing power, but the motor wasn't turning.  So I had to take it apart and clean it again.  This time, I ran it for several minutes with lots of oil in it to get everything well lubricated.  I had disconnected the trumpets so as to not annoy my neighbors during this process.  One thing I did notice was that a couple of vanes had rolled edges where they ride against the top and bottom of the cylinder.  If a vane got stuck in the slot, it could stall the compressor.  So I filed these smooth to prevent that from happening.