kylehq

I'm using a '04 GTO style LS1 and loom in my retrofit. When I have the alternators battery wire connected (the thick red one) my entire loom's constant battery power is connected to ground.

When the alternator is disconnected everything is fine..
I did a beep test with a multimeter between the big battery terminal on the alternator to the chassis and there was connectivity.

I can't figure it out... Why is the constant 12+ terminal on my alternator connected to ground? I'm not sure if it makes a difference but, I haven’t hooked up my brown / white alternator wires to anything yet.

Any help would be appreciated. I’m stumped.

G-Body

iTrader: (4)

Sounds like a bad alt. Even if the brown / white wires are not hooked up the bat constant should not be grounded, that should never go to ground.

the_merv

iTrader: (88)

Ya def a bad Alternator..something's up with it.

Pop N Wood

iTrader: (1)

Take it to a parts store that does free alternator checks.

There are diodes in the output of the alternator. Hook up the ohm meter one way and it is a short. Hook it up the other way and it is open.

Alternator windings have pretty low resistance when the alternator isn't spinning. Are you sure it is zero ohms or just a very low value?

rotor vs. piston

iTrader: (3)

I wouldn't blame the alt' on this. Double check your grounds to chassis and power wires... sounds like you may have something where it shouldn't be.

kylehq

Thanks for the suggestions. I was thinking it could be a grounding problem too but I tested from the B+ pin on the alternator to the car chassis, I dont see how this pin could connect to the chassis other than through the alternator casing. I had all wires to the alternator disconnected.

I was leaning towards a bad diode. This engine came out of a working car so I'm not sure how this would have happened. Maybe I knocked the alternator when lifting the engine into the car?

Pop_N_Wood, is wasnt a 0 resistance beep. It read about 483 I think. I guess the next step is to pull the alternator apart and have a look. Are there any visual signs that I could look for that would cause it to ground like this? Burnt windings wouldn't cause this I guess?

Pop N Wood

iTrader: (1)

Check a repair manual. 438 ohms might be OK. Windings are just a coil of wire. You can expect a low resistance.

A visual inspection can still miss problems. A good repair manual should tell you how to properly ohm out an alternator.

i would take it to a parts place that does free alternator checks first. If something is shorted out it will fail in their machine.

kylehq

Well, I pulled the alternator apart thinking that maybe something had fallen between the B+ terminal and the case shorting it. I couldn't find anything.

What I did discover was that when I measured the B+ terminal to the case with the multimeter probes the other way around it would not find any connection. I guess I was sending the probe voltage through the case and out of the B+ terminal, but it wont go back the other way due to the diodes.

I may have looked too far into this one :S. I'm just going to use it and see how I go.