I was driving home and noticed my voltage was.

Tiny
JESSESANDBERG
  • MEMBER
  • 1980 GMC TRUCK
  • 50,000 MILES
I was driving home and noticed my voltage was running just above 8, all of my electrical wouldnt work (lights, signals, stereo, etc.) I replaced the altinator and battery and it did not change anything, what could be my problem?
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Saturday, April 6th, 2013 AT 8:17 PM

6 Replies

Tiny
CARADIODOC
  • EXPERT
Measure the three voltages on the generator wires. The large output stud must have full battery voltage at all times. One smaller plug-in wire must also always have 12 volts. The other one should have about 6 volts with the ignition switch on and the engine is not running.
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Saturday, April 6th, 2013 AT 8:22 PM
Tiny
JESSESANDBERG
  • MEMBER
On the starter? I do not know what you meant by generator wires sorry. And after I measured the voltage what should I look for afterwards if they read correctly and what should I do if they dont?
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Saturday, April 6th, 2013 AT 8:31 PM
Tiny
CARADIODOC
  • EXPERT
Most people call it the "alternator" but that term is copyrighted by Chrysler. They were the first to develop and use it in 1960.

Besides Chrysler's, yours is one of the best designs there is. GM's newer design starting in 1987 is by far one of the worst ever and they have a huge pile of problems. There are only three wires on yours. Two are plugged in at the back and one is bolted on. Take those three voltage readings with the ignition switch on, engine not running, and holler back with what you find. Measure the battery voltage too for reference.
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Saturday, April 6th, 2013 AT 8:43 PM
Tiny
JESSESANDBERG
  • MEMBER
Battery, 12.3v
Constant power, 12.3v
Brown wire (small) 12.3v
And the other I cant get a reading at all no matter what I try
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Sunday, April 7th, 2013 AT 8:46 PM
Tiny
JESSESANDBERG
  • MEMBER
Well I just diagnosed the problem and it turns out my headers melted the fuseable link that goes from the starter to the altinator, which would explain the no voltage, and the lights to quit cuz there tied in somewhere. Thanks for your help.
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Sunday, April 7th, 2013 AT 10:50 PM
Tiny
CARADIODOC
  • EXPERT
Dandy. Start the engine, then momentarily touch that wire with no voltage to either of the other two. That's easy to do with a stretched out paper clip or a needle nose pliers. Just touch the two wires in the plug together for an instant. If the head lights are on you'll see them brighten up and the generator will keep on working until you stop and restart the engine.

The smaller wire with 12 volts is where the voltage regulator monitors system voltage. The other one is the turn-on signal for the regulator. It comes from the battery light on the dash. If you have only a gauge and no light there is a resistor on the cluster to take the place of the light.

Once the unit is working you will find 12 volts on the wire where voltage is missing now. That is what normally turns the dash light off right after the engine starts.
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Sunday, April 7th, 2013 AT 11:02 PM

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