[Vwdiesel] alt light not working/stoplight problem

[LBaird119 at aol.com]

I also have a weird problem with 
the passenger side stop/running light.  Each works independently but if 
the running lights are on and then you step on the brake then the 
running light goes out and you get no light at all.  I plan on pulling 
the socket and see if there is a cross short between the two wires some 
how.

  This is when you get GOOD at reading a schematic!  Stuff like this is 
usually from "feedback."  We've all become accostomed to AC that we 
tend to forget that DC works differently.  You can have a short that's not 
quite a short.  It'll supply power but only directionally so no fuse blows.  
Instead you get mysterious power supplied to circuits that are "dead."
  Often is the case when you turn the power ON to the supplying circuit, 
then you loose the ground it was providing and the "dead" circuit is dead 
again.  Frustrating until you find the culprit.  Then you feel pretty darn 
smart for finding it and dumb that it took so long!  Just a thought that it 
might be more likely that you're MISSING a ground connection to the 
brake lights and it's pulling it's ground from the lights until they are 
turned on.  

  Alt light gets power from the small wire going to the alternator, sort of.  

It's the ground for it until it starts putting out power, then it looses the 
ground and becomes positive, no current flow, no light.  You said 3 
plugs so I'm assuming it's the 3 wire single plug rather than the lug for 
battery.  Two of them go to the battery and I think the third goes to the 
alt light.  Check for power when there shouldn't be and continuity to the 
alt light.
     Loren