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Anonymous Posted on Mar 06, 2017

I am still fighting an intermittent charging problem on a 1990 GM K1500. It will charge fine then discharge. Doesn't make any difference if in town or on the highway. I've tried three alternators, different battery, I've jumped between all the wires and no luck. The one thing I have found is the brown wire that clips on the alternator and comes from the instrument cluster has erratic voltage levels. When it is charging properly I took the wire off and had a voltage of 12.5 volts. When it wasn't charging properly it only had 2. to .5 volts. I also checked the voltage while the wire was attached and charging properly and it read 13.9 volts and at the battery it was normal 14.5 or so. I'm about at my wits end. My question is, is there something in the instrument cluster that regulates the voltage in this excite wire that could be failing and causing the voltage to drop, thus loosing the excite and causing a discharge, then somehow it finds the right voltage and excites the alternator again? Thanks for your help! Steve

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Jeff Armer

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  • GMC Master 15,575 Answers
  • Posted on Mar 06, 2017
Jeff Armer
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Sounds to me you have high resistance problem , Main power feed to the alternator . Check the power junction block behind the brake booster on the fire wall . There is nothing in the instrument cluster to regulate voltage .B+ voltage to battery symbol when key is on , then when it starts voltage from voltage regulator inside alternator goes back on that circuit shutting off the light . Voltage on both sides of the light cancel's each other out . Yes, i would look for a burnt connector . at the junction block . Do a voltage drop test while the vehicle is running . Voltage Drop Testing the Charging System

2 Related Answers

Anonymous

  • 373 Answers
  • Posted on Jul 06, 2008

SOURCE: alternator not exciting

Hi ' If you changed the battery and alternator,
Check the voltage at the red wire on the alternator. if there a less than 12 volt.
Check the fuse link, that goes in the starter positive bolt.
If the fuse is bad replace and recheck the charging system.
IF charging normal. good.
If not, che the fuse in the fuse box, "" cluster".
If the fuse is blow out, replace. and check again.

OK. I hope this work for you.

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Anonymous

  • 115 Answers
  • Posted on Nov 21, 2010

SOURCE: Intermittent Charging Problem. I posted a

When you wire it in, run a hot wire directly from the battery to the volt meter (this will give you a more accurate reading) The instructions will come with the volt meter on how to wire it. Just make sure about the hot wire coming directly from the battery.

What I would do first is take off the alternator and go to a parts store and have them test it for free. This will save any additional purchases. Good Luck.

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