New alternator not charging

This has been plaguing me for some time now, and I'm finally ready to admit I need help. After finally getting my engine installed and running, the ALT light came on, and I confirmed the battery was not charging. So I took the alternator to A Zone and had it tested. It tested good, so I replaced the repro voltage regulator with an electronic one from Advanced Auto. Light stayed on. I then replaced the alternator and voila, no light!

Thinking that my problem was solved, I re-installed the repro regulator after re-installing the engine (it was out having a leaking rear main seal fixed). Of course in removing the engine, the alternator was disconnected and had to be reconnected. Having done more than one thing before starting the car again, I can't be sure what I did that changed anything, but the ALT light is back on and the battery is not charging. I also added a Painless relay harness for H4 halogen headlights. The lights are nice and bright, but really suck the life out of the battery without a working alternator. Tracing the circuit on my 69 wiring diagram, I can't see where the ALT light picks up ground. Both sides appear to go to battery power.

The car is once again up on ramps, and I'll be checking the ground connections at the block. If anyone has experienced a problem like this before, please jump in to let me know what you did to solve it.

Thanks in advance for any help!

Thanks for the reply bnickel.

The battery is not charging, so the light is useful. I was hoping that if I can figure out where it picks up ground that will indicate what is going bad. Either something in the voltage regulator or something in the alternator must go to ground to generate the light.

BTW, I did ring out the alternator harness and it checks good. I have continuity on every wire, and no shorts between wires. Since my alternator is indicating a hard failure rather than intermittent, I should have been able to detect the cause if the harness was at fault. Thanks for the suggestion though.

It may just be a crappy rebuilt alternator that didn't last very long. I'm going to return it to Advance Auto and cross my fingers and hope the next one lasts longer.

Owe you a beer!

OK bnickel you called it!

I just went and checked the voltage at the field terminal with the ignition on and there was none. So I backed up to wire 904 (green w/ red stripe) coming from the firewall to the regulator and I had 11 volts. Then I plugged the harness in to the regulator and took a reading on the field excitation wire 35 (orange) and I still had 11 volts. Then I disconnected the alternator harness and took a reading at the junction. Still reading 11 volts. Why did I save the alternator harness for last? Because I swear I checked it days ago when I first started having a problem. Lo and behold, it is open between the pin on the connector to the under-dash harness and the terminal that mounts to the alternator. Now this is a brand new reproduction harness, that just happens to be a POS!

So once again I remind myself that just because it's new doesn't mean it's good!

Thanks bnickel, and the next time I'm down in Texas I'd be glad to buy you a beer!

BUYER BEWARE

bnickel said:

hmmm, well i don't drink so we'll call it a coke, how's that? glad you got it fixed... i hate electrical problems personally

Click to expand...

Coke it shall be.

After further investigation I found that the repro alternator harness was made wrong. The 35 (orange) wire is routed to the stator terminal and the 4 (white w/ black stripe) stator wire is routed to the field terminal. I'm sure mine is not the only one that was made incorrectly, so BUYER BEWARE!

If anyone buys an alternator harness you need to ring it out per the print before you install it. Better yet, before you even take possession of it. When I first rang it out I was just going by what I could see. I checked both ends of the orange wire for continuity... not for correct terminal location.

Hopefully this is the last hurdle before I can begin using this as my daily driver. At least when the weather is nice.