mitchntx

Background ...
It's a 96 stock LT1 road race car. It has been completely rewired using a Painless engine harness. The engine harness has no provisions for a charge circuit. It has been near flawless for 3 years.

The charge circuit and exciter field circuit are as follows ...
Battery to master disconnect ... master disconnect to a bulkhead pass through at the firewall ... and the bulkhead to the alternator output post.
The bulkhead connector also feeds the accessory fuse bus, which one circuit is the 12V source for the Painless harness.
I use the ignition circuit to power the field exciter of the alternator. When the toggle switch is on, it sends 12V to the altenator terminals on the master disconnect and from there to the exciter pin on the alternator.
When the master switch is switched off, it kills power to the fuse bus and all electrical circuits connected to it.

I'll run down the list of things we did ...

New motor (including new coil, GM opti and MSD C&R), 1st race. Motor has about an hour of run time on it from a DE the weekend before.

Practice ... OK
Qual 1 ... after about 4 laps, started missing and banging in 4th at anything above 5K
Post Q1 ... went to the scales ... motor wouldn't turn over. Low battery.
Pre R1 ... battery on charger. Install spare#1 alternator. Spare#1 tested good at NAPA. No charge output.
R1 ... with a couple laps to go, started miss-firing again. Won the race, though.
Pre R2 ... battery charging. Removed Spare #1 and installed Spare #2 (Thanks James). No charge output. Stole alternator off of a competitor's car and got ~14V (reinstalled it on Steve's car). Borrowed a fresh battery (Thanks Frank).
R2 ... car ran fine. Found alternator at local Autozone.

Went to AZ ... Spare #1 tested GOOD, but new alternator FAILED.

End of a long day ...

Sunday ...
Q2 ... overnight charge of battery and made the session without a problem. Unfortunately, James did and caused him to load up to make the long trip home. I talked him out of his alternator ... #5.
Pre R3 ... installed Alternator #5 (original no charge, Spare#1 no charge, Spare #2 no charge, pilfered alternator charging) ... no charge.
R3 ... battery only and it made it for a 40 minute race. It was beginning to miss on the big end again with 3 or 4 laps to go. But, I finished. I ran nothing but ignition ... no gauges, no fans ... bare minimum. I started to unplug 3 of the 4 tail light lamps, but decided against it for safety reasons.

Other stuff we did during this ordeal and all with multiple alternators ...
ohmed the exciter wire
ohmed the charge wire all the way to the battery
changed pig-tail at the alternator
removed the resistor from the exciter circuit
jumpered across the master disconnect
jumpered 12V straight to the exciter pin of Spare#1 and #5
changed the ignition switch (powers the exciter circuit)
And many other things as we were all grasping at straws.

I've gotta thank Steve, Morgan, James, Al, Glenn, David, Frank, Jeff, Jerry, and I KNOW I'm leaving several someones out. Lot's of elbows pouring over my car.

Yesterday ...

Unload car, get a reman alternator from Autozone, it tests good, install it ... charging at about 14V.

This was really a weird, frustrating issue. What is crazy is that of 5 alternators, 2 of which were on running cars, only 1 gave any output voltage.

FYI ... I can now change an alternator in 3 minutes ...

FYI2 ... I had no voltmeter in the car. It does now.