1992 Chevrolet S-10 Undercharging

REZA3AUTO

MEMBER
1992 CHEVROLET S-10
2.5L
4 CYL
2WD
MANUAL
240,000 MILES

First, battery light came up.

Second, replaced alternator voltage regulator and brushes with new ones, but left old diodes.
After starting the engine, it was good a little bit, but one of the head lights gone soon after, then voltage dropped down, the only head light and instrument lights dimmed and a weak " battery light" came up again all with the engine was still running.

I think the regulator is ok, because it's supposed to limit high voltages not lows.
My question is, if it's the cause of worn out stator/rotor windings or armature's collectors?
Or it's not alternator's problem?

4 Replies

HMAC300

MECHANIC
48,601 POSTS

What kind of volts it's putting out first it should be about 14.5 maximum. Check ign/gauge fuse in fuse block see if it's ok. Also check condition of battery including load test. Auto parts does for free

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Tuesday, November 18th, 2014 AT 6:32 PM

REZA3AUTO

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11 POSTS

I did not check voltage before it was undercharging, but the instrument voltmeter showed above 13 volts and all the things were good until a weak battery light came up soon and voltage dropped below 12.

I assumed the reason was the rectifier which was not changed, so went to replace that also, but nothing happened.

Checked the voltage with the engine running and it was 11.70 volts.
All the fuses are ok.
Tested alternator with another battery, same issue.

The strange thing that I noticed today is the weak and flashy battery check light, was there with both switch on > engine off and with engine on !

Because with switch on > engine off situation, there is a path to ground through regulator. It means that something is wrong with regulator again.

In cs - 130 manual, I read if there is a problem with the armature like open some were in it's windings, it can damage the regulator.

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Thursday, November 20th, 2014 AT 12:12 PM

HMAC300

MECHANIC
48,601 POSTS

Check the fusible links I have pointed out in pic not the 4amp fuse. Then make sure you have agood ground going to engine block from battery, same to body and same engine to body usually a ground strap back of block to firewall. I don't think it's an alternator problem. I think one or more of your fusible lnks are bad and not giving alternator the power to make it charge.

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Thursday, November 20th, 2014 AT 1:20 PM

REZA3AUTO

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11 POSTS

Thanks a lot for your responses.

Problem solved and again it was a faulty regulator. Despite it was new, but as soon as working for some seconds, it went bad. The circuit inside it, did not allow ground to reach instrument battery light when ign switch was on and so on when engine was running, there was not enough ground for the alternator to work properly.

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Saturday, December 20th, 2014 AT 3:22 AM