Quick Question: Generator Light and Blue Wire

[rockaria]

Hello,

I have a 1978 SC. The Generator light does not come on when I turn the key on. I know it should just like the oil press light does. Every now and again it will come on and then go out quickly.

I took the gauge out of the dash and tested the wires.

The red wires have the 12.5v just like they should.

BUT The Blue Wire ALSO has 12.5V on it. And the battery is getting charged just fine.

Can anybody tell me what would cause 12.V to be on the Blue Wire in this situation. Isn't that a grounding type wire from the Alternator??

Thanks,

[wswilburn]

The field of the alternator is energized by the blue wire through the indicator bulb. I would think you should see 0V (or something small anyway) on the blue wire with the engine off, 12V or so with the engine running. If you see 12V with engine off, there is no significant current flow through the bulb (that is why it doesn't light), meaning you are not energizing the field of the alternator. Could be a bad connection, problems inside alternator or voltage regulator. I would expect to see problems charging the battery, though.