Volkswagen: 78 Bus - Backup Lights Cause Stall Out In Reverse?, strange coincidence, first failure

Question
Hi Rick,

I'm experiencing a very peculiar thing. All of a sudden my bus will stall out when I put it in reverse. A friend told me to disconnect the two wires from the switch on the transmission housing and it worked. Now what? Should I leave the wires disconnected or is there an easy way to find the short?

Also, strange coincidence (or maybe not) my brake lights don't come on. New bulbs haven't changed anything. The tail lights come on when I turn on the head lights, but no brake lights. I've checked the fuses and I was told to check the connection at the master cylinder. If I touch the 2 wires together, will they tell me if the switch has failed by lighting the brake lights?

I've just bought brand new tail light assemblies so I plan on swapping them out once I figure out my problem.

Thanks for your excellent advice.

Bob


Answer
Bob,
I believe the transmission switch or one of the reverse light circuits are shorted to ground.  The power to the reverse lights comes right off the ignition coil power, very coincidental.  If the ignition coil gets grounded, you stall the engine.  However, what is odd is that fuse S21 should have blown immediately the first time this problem occurred.  Maybe the fuse has been bypassed (aluminum foil?) because someone could not keep it from blowing, while the REAL problem (the tranny switch or a frayed wire after it) was not found.
 As far as the brake lights, I don't believe this is related.  Yes the switches at the master cylinder could cause this, but there are two and they BOTH have to fail to get no brake lights, which would be unusual, unless one was bad before and now the second has finally failed also.  In addition, you should have gotten the "dual brake warning" an indicator on the dash on the first failure, but if BOTH fail you will not get any indication.  In troubleshooting this, if the power from fuse S11 circuit were faulty, the horn would not work also.  Yes, you can short the the BLACK and BLACK/RED wires from one of the master cylinder switches to see if the lights come on.  If not, the BLACK wire is a good place to test for 12VDC with a multimeter or test light.  If everything tests good all the way to the light sockets, check to make sure the light housing has a good ground (metal to metal contact, no rust.)
Let me know how it goes.
- Rick