[Vwdiesel] Electrical problem

[Erik Lane]

Today my wife got stranded at a voice lesson with our 81 jetta diesel. She
got in the car to leave after having been there for 90 minutes and when she
turned the key nothing happened. When I got there to tow it home I figured
it might be a bad connection somewhere and I would be able to use jumper
wires to at least crank the starter, but there was nothing. When I put a
meter on the battery all I got was 0.35V!!

The clock stopped 30 minutes after she got there, so something managed to
completely drain a relatively new 900CCA battery in roughly 30 minutes. None
of my fuses are blown, either.

Seems to me that nothing would be able to drain it that fast without popping
a fuse if it was a fused circuit. The only unfused circuits that I can think
of are the starter, glow plugs, and the alternator. When I have the battery
cables disconnected I get a reading of open circuit - so there's not an
obvious short. I thought maybe the alternator has a bad spot and it moved a
bit in all the work I did towing it home and getting it on and off the tow
dolly. But I took the drive belt off and turned it slowly by hand while
watching an analog meter on the ohms setting, and the needle never so much
as wavered. I checked the meter to make sure the battery in it was good, and
if I turned on a light switch in the car the needle swung full field to
zero.

So I'm left with the conclusion that either it's a strange intermittent
problem, or it's the battery, or possibly checking the alternator like that
is not very conclusive. I have the battery on a small 6 amp charger right
now, and it's been on that charger for a couple hours, but it's still
drawing the full 6 amps. If it stays like that for very long then I'm going
to start suspecting the battery of being bad, but like I said it's
relatively new, still under full warranty. So I would be glad if that's all
the problem was, but I would also be surprised.

Can anyone see something obvious that I'm missing? I need this car to be
reliable, so I don't want to just put it back together without having found
what did this in the first place and fixing the problem. Is there a better
way of checking for an internal short in the alternator? It's also only a
couple years old, but it seems to work fine. In fact the car has been very
good and absolutely reliable for us for many years up to this.

Thanks in advance!
Erik