[urq] Alternator light question

[Wbremer]

I experienced the problem with my '82 Euro urq.  The problem of the dim
alternator bulb plagues a lot of early VWs, Porsche 914s, and Audis that
have the pin-type, under-dash fuse box--for urq owners, the "pre-1983.5"
cars.  (I have not heard of the problem with the later under-hood fuse-boxed
cars.)  While the article from the link below may not speak to the specific
problem of a dim alternator warning light, it describes the purpose of the
bulb and its circuitry.  The article notes that the D+ (exciter) terminal
and the B+ (output) terminal produce the same voltage when the motor is
running and an otherwise OK alternator has been "excited" and is spinning.
  
My experience is that the problem lies in the circuitry between the B+
terminal of the alternator/battery and one side of the warning bulb circuit.
The B+ circuit plugs into the back of the under-dash early fuse-box (the
middle of the five pin/socket connectors, as I recall), so if there is any
electrical resistance at that plug/pin connection at the back of the
fuse-box or within the fuse-box from corrosion, then there will be the
slight voltage drop on that side of the circuit when the motor is running
and the warning light will glow dimly.  [The D+ circuitry is a low draw line
from the D+ terminal to the other side of the alternator warning light.]  In
this circuit, the warning light is "off" when there is +12 v or so on both
sides of the bulb.  The problem is most likely with the B+ "side" of the
warning light circuit wiring, most probably at or within the fuse-box.  We
all know the fuse-box is grossly inadequate to carry the current flow
required by the urq's electrical system and is the reason that many of us
have run separate circuits from the B+ terminal or the + battery terminal to
run high-wattage headlights, the fuel pump and even the rear window
defroster.

In my situation, I had the problem develop even after replacing the original
fuse-box  with a new one.  I subsequently found that the main power plug had
overheated and melted a bit and the plug sockets had blackened a bit.
Cleaning the pins and plug sockets, adding some Wurth Contact OL and very
firmly reseating the plugs virtually eliminated the faint glow.  My $0.02 is
that if that alternator bulb glows at all--and in particular if it is
anything but very, very faintly at night, that's a symptom of a problem with
the main power plug into the back of the fuse-box, and one day it will just
shut down power to the entire fuse-box, including the ECU: the engine shuts
down without warning and there is no electrical power to the car.  The
engine will probably not restart, although sometimes after ten-fifteen
minutes the plug or fuse-box cools down and electrical power is restored for
a while.

http://www.pelicanparts.com/techarticles/914_alternator_troubleshoot/914_alt
ernator_troubleshoot.htm


Bill
'82 Euro