Alternator confusion..

[Tom Mandera <tsm1@domain.elided>]

Alright, as I explained earlier, I left for Missoula on Thursday, and all 
was fine.  As I neared Missoula, the alternator gauge was flickering in 
the Charge area.  It's been known to move a little with bass hits from 
the stereo (the audio gear is all wired to direct to the battery via a 
relay), but this was different.  This was more like the fun wiggle of a 
speedometer when the cable has a kink.  I couldn't really determine if 
there was a *pattern* to it or not (like, if I hit a bump, it would work 
OK or... I didn't notice anything like that)

When I pulled off the Interstate and approached the stop sign, the 
AMP gauge went deep into the Discharge.. and I thought the truck had 
stalled 'till I hit the accelerator.  It then continued to charge and 
discharge as I drove across town.  

It did this again over the weekend.. though it seemed if I revved the 
motor high enough, the alternator would charge, but still flicker or 
"twitch".

I left for Helena this evening.. and the alternator gauge was bouncing 
around in the charge area.. and then would fall into the discharge realm 
for a while.. then work.. then not.. then it didn't for about 40 miles or 
more.. nice, dim headlights.. then I downshifted to 3rd and stood on the 
gas, and the alternator worked again - bright headlights and a bouncing 
Charge needle.

Going down the pass, at times I would have the motor racing and the gauge 
would show Charge, and at times I would have the motor really low, and it 
would indicate a charge.. put the revs in the middle, and discharge.

When I pulled into Helena - discharge.  The gauge hasn't shown a charge 
since.

After changing out the heater core and assembly, I yanked out my 90amp 
alternator and replaced it with a 63amp unit I had on the shelf.  Recall 
that I have onboard air and pieces of the AC system.. what fun it is to 
change an alternator!

Changed the alt out, started the Scout.. discharge.  Pull the headlights, 
discharge.  Kick on the Daylighters.. still the same discharge 
(ordinarily, if the alternator were charging, if I hit the KCs (wired to 
the batt), the alternator gauge would indicate a heavy charge.. or, at 
the least, the belt would squeal.)

I shut it down and then started following the alt wires.. to the bulkhead 
connector.  I disconnected it, plugged it back in, and tried it again - 
no change.  Still no charge.

Also note that my bulkhead connector (the main one) is actually two 
connectors now.. it's been cut in half, with a left and a right piece, 
while the two center leads have been spliced together directly.  It 
wasn't my idea.. a left-over from the previous owner that I had to carry 
forward when I swapped motors.

At this point, it's 2am, and I need some rest before work in the AM. 
:-)   So I put the charger on the battery, and resigned myself to driving 
to work on just the batt.  The Die Hard of unknown vintage did fine with 
the headlights on racing across the Interstate.. a quick trip across town 
should be do-able.

But... where do I go next?  A loose belt has caused *some* of the 
symptoms I described... like the sporadic charge/discharge depending if 
the belt has "grabbed".. but the belt was (and is again) tight.  I 
changed the alternator, so that's not the culprit.

My first thought was a massive short.. possibly brought about by the 
shovel under my hood that has been known to chafe some insulation 
(haven't gotten to my permanent fix.. for a while, I left the shovel out, 
but I was fourwheelin' not long ago).. so I took the shovel out and 
looked for damaged wires at the brake booster - I didn't see any.

Hmm.. heater blower motor all wet from the heater core rupture?  Not any 
more.. whole new motor and everything...

The power lead from the stereo to the amplifiers that was acting funny 
the other day?  That's only an issue when the stereo's on.. it wasn't.

Antifreeze leaking under the dash into something?  I haven't checked that 
yet.. 

Is this a bad voltage regulator?  Do they fail in a manner like I described?

Just wondering what to troubleshoot next.. I'd like to get this patched 
up tomorrow evening after work.. and then test out the heater.

-Tom Mandera, Helena MT
http://www.tmcom.com/~tsm1/scout