77 Bus, Regulator or Alternator?

[mentalQtip]

Ok. 1977 fuel injected bus. Alternator light is gently glowing when the engine is running and the battery is definitely slowly discharging.
I started at the regulator and found, engine off D+ at .45 volts
Df at .45 volts
engine idling D+ 13.3 volts
Df 4.8 to 5.3
high idle D+ 13.3
Df 2.2
How do I interpret these numbers?
Bad regulator?

Thanks

Joseph

[dingo]

well for starters, if youre getting 13.3V at idle, then the alternator and regulator are functioning reasonably well. (at idle)
As for the dash light glowing, im going to guess that is resulting from one of the several diodes in the alt going bad.,.allowing some unrectified voltage to get up to the dash.. Does the light glow when you have higher rpm ?

[mentalQtip]

The dash light does not change with higher rpm. When I turned the headlights on the glow was even brighter. Shouldn't the D+ reading be more like 14volts, and the voltage at Df with higher rpm actually went down.

Joseph

[Amskeptic]

The dash light does not change with higher rpm. When I turned the headlights on the glow was even brighter. Shouldn't the D+ reading be more like 14volts, and the voltage at Df with higher rpm actually went down.

Joseph

Sounds like an alternator diode if you .45 v when off.
Colin

[dingo]

set Meter to AC volts, red lead to D+, black lead to ground. Good alt read less than .5V

[mentalQtip]

I read 29volts on the 200AC setting.

[dingo]

sorry i meant B+ , not D+ ( i was working on a generator today and confused myself)

anything above .2 is suspicious.......