Tim:

I have looked at the schematics for the 1988 and 1996 trucks. Neither
one shows a relay. I suspect that the relay is unrelated to the charging
system. This would explain why it is not shown in the (charging system)
wiring diagram. The relay clicking off is probably just a symptom of
the charging system not working.

My symptoms have varied over time.

At first the alternator V-belt slipped intermittently despite being
overtightened. Turning off the A/C stopped the slipping. The A/C had
to remain off for up to 60 s before it could be turned back on without
causing the V-belt to slip. Sometimes the battery was too weak to turn
over the starter until the driver opened his door and lightly rocked the
vehicle forward or backward in any gear with one foot. Battery and (new)
starter were good.

Then the (dashboard) charge warning lamp stayed off all of the time,
even during the bulb check. Battery terminal voltage was lower with
the engine running than with the engine off. The charge warning light
bulb was good. (I confirmed that the bulb was good by grounding the L
connector of the alternator plug with the ignition on and the engine
off.) Replacing the alternator had no effect. The new alternator was
confirmed good with a bench test before installation. The old alternator
was confirmed good with a bench test after removal. During the bench
test the old alternator, rated at 60 A, delivered 90 A of current
without any V-belt slippage.

Later, just before writing my previous article, wiggling the alternator
plug (with the engine running) had the following effects:

       1. relay clicks
       2. (dashboard) charge warning lamp state changes
       3. voltage changes across battery terminals

Now I am unable to identify the clicking relay because I can no longer
get it to click. I can still toggle battery terminal voltage between
12.5 V and 14.3 V by wiggling the alternator plug. Each change in
battery terminal voltage is accompanied by a change in engine sound.

The changing symptoms consistently indicate a bad alternator plug.

Who would have thought that all of the following symptoms were caused by
a bad alternator plug?

       - slipping alternator V-belt
    - difficulty starting
       - alternator warning lamp bulb check failure
    - charging system failure

Who would have known where (http://www.nwreg.com/) to buy a new
alternator plug?

After my mechanic went thru the entire truck, connection by connection, put
meters on every electrical connection he could find, tore out part of the
dash, looking for something wrong.  He finally decided it had to be the
alternator or regulator inside the alternator, so he put everything back
together, installed the 5th alternator, new by the way, it is now charging
like it should.
 I think, but did not tell the mechanic, that it was a wire or ground that
he moved or jiggled, not knowing that was the problem all the time.  I don't
think my problem ever was an alternator.  Installing 5 rebuild/new units
does not make sense........any thoughts on this?  Thanks for all the help
from the newsgroup..........

shaqtopz:

I thought that I was well-prepared because I had bought some Stabilant
22A a long time ago. It has helped me in the past but it did not do the
trick this time.

Does DeoxIT work better than Stabilant 22A?  Maybe.  However, given
that a brand new connector without DeoxIT or Stabilant 22A generally
works well for a long time I assume that the combination of a new
connector and Stabilant 22A will work better than a combination of the
old connector and DeoxIT.

Here somebody recommends a combination of DeoxIT and Stabilant 22A
for use on computer connectors:

       http://mindprod.com/bgloss/contacttreating.html

The ultimate solution for my problem would probably be a combination of
a new connector, DeoxIT, 99% isopropanol, and Stabilant 22A but I hope
that I will not have to go that far.