[killakev]

I have a ’68 Firebird. Had a Chevy small block when I bought it, drove it a couple years with no charging issues. During last winter I removed engine and install correct Pontiac motor and used the same Generator that the car previously had. I did do some wiring repair mainly putting the neutral safety back which was bypassed. Car has original wiring harness and the repair mentioned was put back to original specs. This car has an external voltage regulator with a generator.

Problem now is that the charging system is not charging the battery – only 12.5V coming off the generator post when running. I did buy a new generator but I was getting the same result – not charging. So I returned the new alt and installed the one I was using. Below are test results after probing the generator, battery and voltage regulator and I attached the shop diagram for reference.

Generator Car Running
Key OFF Key ON (harness unplugged from Alt.)
1 (BLK WHT Stripe) 0.0v 0.0v 0.06v
2 (DRK BLU) 0.0v 11.9v 11.8
Post 12.5v 12.5 12.4
Battery 12.5v 12.5 12.5

Voltage Regulator
Position Wire Color Key ON Car Running
1 DRK BLU 11.9 11.8
2 BLK WHT Stipe 0.06 0.06
3 ORG 12.4 12.3
4 BRN 5.92 5.84

Looking like there is a problem with No. 1 position wire (BLK WHT Strip) not getting voltage? Voltage regulator problem? What do you think? Suggestions?

[killakev]

Adding diagram

[killakev]

I swapped out the voltage regulator today from my other car to test in the Firebird but no change

[johnta1]

The Blk/Wht stripe wire should have 12 volt when key on.
The Brown wire to the regulator should have 12 volt also when car on I think.

Does the car have the idiot light for the alternator?
Is it lit up when running?

Make sure the wires and connections are good, not loose.
Have you had the cowl wiring connectors apart?
(the connectors with a lot of wires)

[killakev]

Originally Posted by johnta1

The Blk/Wht stripe wire should have 12 volt when key on.
The Brown wire to the regulator should have 12 volt also when car on I think.

Does the car have the idiot light for the alternator?
Is it lit up when running?

Make sure the wires and connections are good, not loose.
Have you had the cowl wiring connectors apart?
(the connectors with a lot of wires)

The BLK/WHt stripe wire, which is in the #1 slot on the back of the alternator has 0V with the key on. The DRK BLU wire (#2 slot) has 12v with key on.

BRN wire with key on has 12v at the V. Regulator with the key on. When the car is running, it measures 5.9v.

The car has rally gauges and I don't see it move, it's sitting right in the middle. Sits there even when car is running and headlights on.

No, I havent removed the bulkhead connectors on the cowl. I tested continuity of the BRN wire from the fusebox to the V regulator and it's good.

[johnta1]

What is the alternator #?

[killakev]

Check this out - I pull the directions out of the box of the new alternator I bought and haven't returned yet....found this in the instructions "Start the car and allow it to warm up. Attach multimeter to the battery and bring the motor up to 2000 RPM. You should have voltage readings of 13.5 to 15V."

So I started the car, hooked up the multi meter to the battery then brought the motor up and over 2000 rpm. BANG the reading went from 12.5V and jumped to 14.2 and stayed there! I hope that it's at 14+ went I start it tomorrow!

[johnta1]

The alternator needs to be 'excited' to start charging. Usually the higher revs will get it going. The field wire wasn't high enough to get the regulator to activate until the rpm's went up.


Anyway, hopefully it's OK now!

[killakev]

It's charging now. just a strange thing I think