ignition switch on no alt. sense power

Len

New member
Aug 25, 2019
5
0
1
I have 12v at alt. sense with ignition off, and no power when ignition in on position. This causes the alt. to output high voltage. Has anyone seen
this problem or cure?
--
1977 26 foot, royale
Alamogordo NM
 
Brown wire is the field excitation voltage to get the alternator starting to produce power. It has an in-line 10.0 ohm resistance and if you were
using it for ground on your voltage measurements, that's why it looked like the voltage sense line (white) when to ) volts (they both had 12V on
them!

The brown wire should have something less than battery voltage with the key set to Ign. Wite wire should have battery voltage on it.

When running, if you have an Isolator (as OEM) then the output of the alternator should be 0.7 volts higher than the battery voltage.

--
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
 
Thanks, for all the info. I also found a miss wire onthe isolator. Seem to
be working fine now.

On Wed, Sep 11, 2019, 4:52 PM Bruce Hislop via Gmclist <

> Brown wire is the field excitation voltage to get the alternator starting
> to produce power. It has an in-line 10.0 ohm resistance and if you were
> using it for ground on your voltage measurements, that's why it looked
> like the voltage sense line (white) when to ) volts (they both had 12V on
> them!
>
> The brown wire should have something less than battery voltage with the
> key set to Ign. Wite wire should have battery voltage on it.
>
> When running, if you have an Isolator (as OEM) then the output of the
> alternator should be 0.7 volts higher than the battery voltage.
>
> --
> Bruce Hislop
> ON Canada
> 77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.1 ton front end
> http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
> My Staff says I never listen to them, or something like that
>
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