Re: Electrical Poltergeist II: A Different Daemon

[ChuckKuecker <ckuecker@mcs.net>]

At 16:34 1/1/98 +0000, you wrote:
>Hey, again, folks. . .
>
>I have a new electrical problem on my '81.  I installed a new voltage 
>regulator a week or so ago, and then a new battery.  Now, the car 
>will start just fine and idle for about 10 minutes.  Then, it 
>suddenly dies and the battery is dead.  A set of jumper cables will 
>start the car, but not revive the battery.  Driving won't help the 
>battery, either.
>
>The first time, I returned the battery to the store, thinking I had 
>somehow gotten a bad battery.  The salesman tested it, said the 
>voltage was OK but the cold cranking amps were way down.  The newest 
>battery did the same thing, though.  The salesman tested the charging 
>system on my car, and said that the gauge went from 3 volts to 7 
>volts to 14 volts, each time making a sudden jump.  These jumps occur 
>in no particular order.  He said it could be a bad alternator, or 
>possibly a short.  He said when he removed the clamps from the 
>battery, there was a spark at the positive terminal (with the car 
>running).
>
>Do I have a bad alternator or a short somewhere?  Other than the 
>charging system, everything electrical on the car works flawlessly.
>
>It's an '81 Scirocco, 5-sp tranny, AC.  The alternator is a Bosch 
>with external regulator--which leads to another question.  I have a 
>Motorola with internal regulator on my '77; will it work on my '81?
>
>Thanks in advance!
>
>Carlee

How long does the battery hold a charge? If it goes flat overnight, or
quicker, you probably have a drain (short) somewhere.

If the charging voltage is jumping around that violently, and the alternator
tests good on a test stand, you have a wiring problem. Look at the harness
between the regulator and alternator first, watching for corrosion or loose
wires. I assume this test was done with the motor running, and not during
cranking.

The next thing to try is to remove the positive cable with all switches off.
There should be no sparks when the cable is touched to the terminal on the
battery. If there are sparks, you have a short somewhere.

The starter could be a problem. I have seen units that crakned OK, but drew
massive overcurrents while doing it.

To check if the alternator is draining the battery, disconnect the heavy
lead at the alternator and touch it to the terminal you just disconnected it
from. A good alternator will not draw any current, and will not spark. Be
careful not to ground this lead to anything while you try this test!

An in-line ammeter can also be used. Disconnect one of the battery cables
and hook the ammeter between the cable and the battery. Normally you should
see only a few milliamps drain for things like the clock and radio memory,
if all loads are off. If there is a larger drain, remove fuses one at a time
to try and isolate the shorted circuit.

Chuck Kuecker

ckuecker@mcs.net

'83 Scirocco (Katy's car now)
'58 Ghia Convert
'75 Bug
'67 Bug
'63 Bug (*still* for sale)
'91 Vanagon


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