'86 5KTQ: Bad alternator or voltage regulator?

Peter Golledge petergolledge at gmail.com
Tue Mar 11 20:19:33 PDT 2008


I suspect the battery cable "splice" at the firewall... common failure on
Type 44.

Start the motor and compare the voltage a the battery terminal with the
voltage at the jumpstart post.

You can also check the voltage difference between these points when
starting.  A large difference means that the splice has a high resistance
and is likely the reason for your issues.  You can search on Audifans for
finding/fixing the splice, its under the carpet near the firewall in the
passenger footwell.  For the three cars I've fixed I used a splice from home
Depot which was intended for high current mains wiring.

-----Original Message-----
From: quattro-bounces at audifans.com [mailto:quattro-bounces at audifans.com] On
Behalf Of L DC
Sent: Tuesday, March 11, 2008 7:53 PM
To: quattro at audifans.com
Subject: '86 5KTQ: Bad alternator or voltage regulator?

I drove my '86 5KTQ last week for about 1 hour, traveling some 35 miles
including stop-and-go traffic as well as some highway driving.

I pulled over to a gas station to fill up some gas and when I tried to start
the car, the battery did not have enough juice to crank engine over. I
jumped started the car but it die after driving some 90 feet away. My
brother brought over a spare battery and made it home, which was some 5
miles away.

I took the battery to Advanced Discount Auto Parts was told it was good but
needed charging.

With the battery fully charged once again, I tested the battery before I
started the car and it showed
12.6 volts. It also showed the same voltage at the starter and big threaded
rod on the alternator.
However, power would declined as time went on and under load when the
radiator fan came on and some 20 minutes later, while idling while I tested
things out, the car die.

Battery once agai was drained to 11.25 volts and, thus, car would not start.

I took the alternator off the car and had it tested at Advance Discount and
was told that it is good.
However, I don't know if the test was properly done.
For instance, when the guy at the store hooked up the testing wire to the
bigger threaded rod to which the big wires in the car attached to, no power
was evident--dead. When he hooked it up to the small threaded rod to which
the little wire attaches to, power was evident in the area of 15-16 volts,
so he said alternator was good.

I had one of the alternators they stock tested and it yielded the exact same

Not confident on their results, I had the alternator tested at an
independent shop and the guy there told me it was good too, but I did not
see the test itself.

The wiring from the alternator to the starter looks fine.

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