[Vwdiesel] electrical troubles

[Sandy Cameron]

At 05:39 PM 1/20/2010 -0800, you wrote:
>  Does anyone know where I can find a wiring diagram (schematic) for an 
>'84 Rabbit "L" diesel?  I have the Bentley Rabbit/Jetta Diesel manual 
>but none of the diagrams in it are accurate for my car.
>
>  Specifically I am trying to chase down a headlight problem.  While 
>driving on high-beams, the headlights will blink off and on a few times, 
>and then go off entirely.  They do not go dim or flicker, they just go 
>off entirely.  Driving on low-beams seems to be better -  I have rarely 
>seem the same symptoms on low-beams.
>

That sounds like the behavior of a thermal circuit breaker, but it could be
related to  item 2 below




>  This car has a neat feature -  if I am driving with the headlights on, 
>then stop and turn off the engine but leave the headlights turned on, 
>the headlights will go out when the engine stops but the running lights 
>& taillights will stay lit.  Somewhere there is circuitry which senses 
>that the engine has stopped and shuts off the headlights but leaves the 
>running lights on.

Could be. There is a relay in the relay group, not sure where it is located
on the A1, at your left knee?

One of these relays, with 4 prongs, is the "X" relay (sort of like the X
files) and is powered by its own contact on the ignition switch, in the run
position only. Its purpose is to cut the power to the headlights and some of
the other heavy consumers while in cranking mode.
In later cars, there is other circuitry that causes it to turn off the
headlights when the "ignition" is on, but the engine is not running.

The relay could be a bit loose in its socket, but far more likely, the
problem is at the ignition switch. That contact uses very little power to
operate the relay, and the ignition switch is well known to be a piece of dung.

My approach would be to douse the electrical part of the switch thoroughly
with WD40 while execising it. The offending wire and contact are marked on
the back of the switch with an "X", and the wire attached to it is black
with a yellow tracer .

If the switch is pooched for the X contact (+12v in run position only)
A work-around, which would not shut the lights off while cranking (you can
still do that yourself with the light switch) would be to cut the
black/yellow off the switch, and splice it to the black wire on terminal 15
of the switch. 
There are 5 wires on the back of the switch 2 are thick, red is power in
(12v), Red/black goes to the starter, black/yellow goes to the X relay,
Black goes to the fuel cut-off solenoid and other stuff that needs to be on
for both start and run, and finally there is a thin brown/red that has
something to do with the "you left your lights on, idiot" beeper.

Make yourself a small test lamp. Those wired low voltage flowerbed lights
are 12 volts, attach 2 wires about 3 feet long, pot clips on them if you
want to get fancy and avoid frustration. Ground one firmly anywhere you can
get at a brown wire terminal, or a steel part that is firmly attached to the
body, then go hunting with the other one. It will tell yoy where 12 volts
is, and where it is not.

Happy hunting.