We are into our 3rd engine swap project using the 1995 LT1 drive train.
Our current project is a 1974 Monte Carlo using a 1995 Buick road master LT1 drive train, full computer…
Runs great, starts, shifts, lock up works, no codes, no check engine lights, no drivability problems except that when we connect the alternator harness up to the alternator, the engine stumbles, runs ruff and dies…..

We get 12.8 volts at the bat terminal with out the harness connected. When we connect the harness, voltage goes to 14.8 (like it should) and then it wants to die….

We swapped the alt from the wife’s 95 road master into it and still the same problem. The original alt works fine in her car….

The L terminal is hooked to a 300 ohm resistor then to a keyed inside power source. The I terminal is hook up via the factory wire to the Secondary cooling fan fuse in the under hood fuse box.

We are not blowing a code… and we do not get a check engine light….

We’ve re traced all the wiring, and all connections to the Monte….we re checked all our soldered connections..

It’s damm confounding….

We pulled and cleaned all the ground connections…and we have good pressure and temps…

Any suggestions would be welcome