Need info. Which wire on voltage reg to ground to test alternator.

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340doc

340doc

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I used to know, lol. I remember unplugging the regulator and grounding one of the wires in the plug to ck if the alt is working. Its a 70 Dart. Thanks.
 
Two small wires on alt. Battery +on one and ground the other.
 
Field is shorthand for the copper windings that create an electromagnetic field when electricity goes them.
Power goes in one end at system voltage and out the other at close to zero.
On a '70, the regulator controls the wire connection to ground.
The regulator's controlling circuit uses system voltage.
That's why there are two field terminals and two wires.
 
340doc said:
I used to know, lol. I remember unplugging the regulator and grounding one of the wires in the plug to ck if the alt is working. Its a 70 Dart. Thanks.
Click to expand...

It CAN be, but might not be that simple. You have FOUR circuits, actually, to be technically correct

1...Ground. In the case of these girls, the alternator is firmly bolted, and that is the ground. End of that

2...Alternator output.......the big wire on the big stud. THIS could be a complication. "What if" it has a poor connection/ is open to the battery? You can "full field" the thing all you want and it won't charge

3 and 4....The two field wires. BLUE is 12 TO the field FROM the ignition circuit. Leave that connected

GREEN is the VR wire and that is the one to ground

CAVEAT:

So try grounding the field terminal which was connected to green, see if it charges.

IF the alternator OUTPUT is open, the alternator voltage will go sky high as RPM is increased, without getting to the battery. Therefore, put a voltmeter on the battery, see what happens with RPM, then move to the alternator to make sure it is less than, "say," 2V difference

IF the blue wire circuit is faulty, grounding the field won't make it charge. To find out, turn key to "run" engine off. Ground the field terminal which was green, and use a voltmeter to see ifyou actually have 12v at the blue. Dont disconnect the blue, you want it under load

IF the green wire is broken/ cut between the alternator and the VR, your ground test will show "good" but when hooked to the VR, it won't charge.

To test, do this: Disconnect the VR connector and devise a way to jumper the connector between the two terminals. This will send 12V back to the alternator field on the green. so this time, disconnect the BLUE and try grounding that field. If it charges, the alt is OK, and the blue/ green VR field is OK

The VR MUST be grounded. !!!! MUST!! To operate.
 
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