Diagnosing high voltage

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hotrod swinger

hotrod swinger

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All of a sudden driving voltmeter pegged. Pulled over to diagnose.

With key in start, engine not running, checking all points on the blue ignition circuit for voltage drop and reading is 0.2V.

Where do I go from here?
 
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I followed the FSM instructions to test the voltage regulator:

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Voltage is 16+, too high.

Blue wire reads battery voltage.

Green wire reads 0.6V
 
Mine was the blue wire's connector broken off inside the VR socket and she pegged the meter. Lights on highbeam and drove the Bird home. Repaired with a female connector and all good again. Maybe your blue wire just came off the alternator spade?? or is loose or similar.
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Checked those connections. They look good.

With key on, engine not running, my voltage at the ballast and voltage regulator is 2.0V, at the alternator it’s 2.6V, so I think those connections and numbers are ok.
 
I know next to nothing elec, but 16+, I believe there is poor connections/ground. Alternator is trying to make up for the voltage drops.
 
I ran the engine with the green wire disconnected and the alternator continued to charge the battery, same readings as without green wire connected.

Surely this must be internal to the alternator? Both terminals on the green wire look fine.
 
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hotrod swinger said:
Checked those connections. They look good.

With key on, engine not running, my voltage at the ballast and voltage regulator is 2.0V, at the alternator it’s 2.6V, so I think those connections and numbers are ok.
Click to expand...
You car going to have to define this. You measured from where to where?

If you measured from ballast to ground, "that's very low" (should be "same as battery)
If you measured from ballast to battery PLUS, "that's a lot" (a lot of drop)
=======================================

"The path"

The path for the alternator field is 12V from the blue wire, from the ballast junction supplied to one field--either field---------through the field, out the second brush ---to the green field wire and back to the VR

The VR in essence controls "the amount of ground" the field sees to regulate field current. (It actually pulses so it' s a matter of duty cycle) this is how the VR controls alternator output-----a "harder" ground for more field current= higher output from the alternator

THE FIELD CIRCUIT might have a ground, either shorted green or shorted brush holder, causing the alternator field to see full current through the field, and max output.

Could be bad VR, and in rare cases, bad battery

Again, your voltage readings are confusing. Might still be a voltage drop problem
 
Don't worry about what they are showing inside the VR here, and remember THE VR MUST BE GROUNDED. Wire at bottom left J+ is feed from ballast IE battery voltage

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hotrod swinger said:
That was from battery positive to those two locations. And I made a mistake. The readings were 0.20 and 0.26.
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AH OK then I'd say VR drop is good. Next, make sure the green brush connection is not grounded. Remove both field wires, check one or other brush/ field to ground for resistance, they should be OPEN / infinity. If they are, make sure VR is grounded, and if so, replace VR
 
hotrod swinger said:
I ran the engine with the green wire disconnected and the alternator continued to charge the battery, same readings as without green wire connected.

Surely this must be internal to the alternator? Both terminals on the green wire look fine.
Click to expand...
I missed this, and this should NOT be.
 
  1. What car?
  2. What year?
  3. Square back alternator?
  4. Electronic regulator ( V shaped connector)
  5. Has anything been changed on the car lately?

hotrod swinger said:
All of a sudden driving voltmeter pegged
Click to expand...

volt meter Or AMMETER.

2 different things and have far different pegging causes
 
67Dart273 said:
Next, make sure the green brush connection is not grounded. Remove both field wires, check one or other brush/ field to ground for resistance, they should be OPEN / infinity. If they are, make sure VR is grounded, and if so, replace VR
Click to expand...

Both wires show resistance to ground.
 
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Dana67Dart said:
  • What car?
  • What year?
  • Square back alternator?
  • Electronic regulator ( V shaped connector)
  • Has anything been changed on the car lately?
Click to expand...

73 swinger
Square back alternator
Two wire alternator voltage regulator system
Voltmeter

loads of changes recently, I repaired my wiring harnesses, repaired a bunch of terminals and wires, installed ignition relay, restored all of my factory gauges, etc.
 
67Dart273 said:
AH OK then I'd say VR drop is good. Next, make sure the green brush connection is not grounded. Remove both field wires, check one or other brush/ field to ground for resistance, they should be OPEN / infinity. If they are, make sure VR is grounded, and if so, replace VR
Click to expand...
What 67dart273 was asking...


With BOTH field wires disconnected.
What is the resistance red dot to green dot?

And

Red dot to fuschia dot

Screenshot_20220215-185247~2.png
 
Our messages crossed paths, both terminals of the alternator have resistance to ground.
 
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