77 Bus, Regulator or Alternator?

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mentalQtip
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77 Bus, Regulator or Alternator?

Post by mentalQtip » Fri Feb 12, 2016 7:07 pm

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

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dingo
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Re: 77 Bus, Regulator or Alternator?

Post by dingo » Fri Feb 12, 2016 9:28 pm

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 ?
'71 Kombi, 1600 dp

';78 Tranzporter 2L

" Fill what's empty, empty what's full, and scratch where it itches."

mentalQtip
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Re: 77 Bus, Regulator or Alternator?

Post by mentalQtip » Fri Feb 12, 2016 9:45 pm

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

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Amskeptic
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Re: 77 Bus, Regulator or Alternator?

Post by Amskeptic » Sat Feb 13, 2016 8:10 am

mentalQtip wrote: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
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
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dingo
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Re: 77 Bus, Regulator or Alternator?

Post by dingo » Sat Feb 13, 2016 11:03 am

set Meter to AC volts, red lead to D+, black lead to ground. Good alt read less than .5V
'71 Kombi, 1600 dp

';78 Tranzporter 2L

" Fill what's empty, empty what's full, and scratch where it itches."

mentalQtip
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Re: 77 Bus, Regulator or Alternator?

Post by mentalQtip » Sat Feb 13, 2016 6:49 pm

I read 29volts on the 200AC setting.

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dingo
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Re: 77 Bus, Regulator or Alternator?

Post by dingo » Sat Feb 13, 2016 8:56 pm

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

anything above .2 is suspicious.......
'71 Kombi, 1600 dp

';78 Tranzporter 2L

" Fill what's empty, empty what's full, and scratch where it itches."

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