Generator Output never positive

[btrempel]

Has anyone seen this?

Engine off --> Lights on --> Generator showing -ve (as expected)
Engine on --> Lights on --> Generator does a quick dip to -ve and will sit around the 0 mark.

I've never seen it swing to a high +ve value with any type of electrical load.

thoughts?

[btrempel]

Here's an update for completeness.

Battery was not healthy so it was replaced.
The Generator Diagnosis Procedures section of the Plymouth Service Manual was used and suggested that the Voltage Regulator needed to be replaced. Be aware that if you are polarizing your regulator that you double-check the procedure. The polarizing steps imprinted on my new voltage regulator did not match up to steps found on the Internet.

First test: I measured the voltage on the battery (6.1 volts) and then started the car. The voltage across the battery rose to 7.0 volts.

Second test: With the car off, I left the headlights on for 10 minutes or so. I then started the car. This time the ammeter swung +ve (maybe 10 amps) for a brief time before reducing to about 2 amps or so and then settling back to 0.