Alternator voltage regulator bad?

ldj · May 2, 2022

My GM 3 wire 10 SI alternator not charging. How can I test to see if alternator is bad or if voltage regulator is bad.

wore out · May 2, 2022

(quoted from post at 09:44:47 05/02/22) My GM 3 wire 10 SI alternator not charging. How can I test to see if alternator is bad or if voltage regulator is bad.

First, verify that battery voltage is present at the large output stud and the #2 "sense" terminal AND that "excite" voltage is present at the #1 terminal.

If no charge you can verify whether or not the VR is causing the issue by doing what is illustrated in Figure 5 at the link below. Follow instructions about not inserting a tool too far and hitting moving parts (the rotor).

Other helpful info there, as well.

https://alternatorparts.com/10si-15si-type-116-136-repair-manual-page-3.html

guido · May 2, 2022

ldj

Check battery voltage first. Then start
the engine, you should get about 1.5 volts
above the battery voltage with the engine
running,

Guido.

John T · May 2, 2022

Easy way is check battery voltage. A fully charged 12 volt battery at rest and stabilized is around 12.6
volts........

If hooked to a good working alternator when running subject to RPM, battery and alternator, battery voltage
SHOULD RISE to at least 13 to around low 14 IF SO ITS CHARGING.......... IF NO VOLTAGE RISE ITS NOT

Even with no meter the lights may glow noticeably brighter when running versus not running if charging

John T

JMOR · May 2, 2022

(quoted from post at 12:58:34 05/02/22)

(quoted from post at 09:44:47 05/02/22) My GM 3 wire 10 SI alternator not charging. How can I test to see if alternator is bad or if voltage regulator is bad.

Click to expand...

First, verify that battery voltage is present at the large output stud and the #2 "sense" terminal AND that "excite" voltage is present at the #1 terminal.

If no charge you can verify whether or not the VR is causing the issue by doing what is illustrated in Figure 5 at the link below. Follow instructions about not inserting a tool too far and hitting moving parts (the rotor).

Other helpful info there, as well.

https://alternatorparts.com/10si-15si-type-116-136-repair-manual-page-3.html

ttps://i.imgur.com/WeuUAEM.jpg[/img]

This post was edited by JMOR on 05/02/2022 at 02:50 pm.

Alternator voltage regulator bad?

ldj

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wore out

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guido

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John T

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JMOR

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