Alternator ground question.

[jmbass98]

Having charging issues. Got a new alternator from Layson’s. Has two field posts on the back. Is this the right style of alternator? Does one need to be grounded to the case for proper function? If so. What gauge ground wire to use?

Points. Mechanical voltage regulator. ‘66 Charger.

 

[RemCharger]

Are both of the terminals isolated ? Or is that top one screwed to ground. Hard to see.
Fibre washers between screw and terminals

 

[RemCharger]

14 g

 

[Don Frelier]

Looks like a dual field isolated.
I would suggest installing a solid state regulator and running the extra wire to the alternator.
You would need the plug for the solid state of course as well.
But they put out more current at lower RPM which is a good thing with a Charger with all those brake lights.
A #16awg would be adequate for the field wiring.

 

[jmbass98]

Okay. I spoke to a alternator rebuild guy near me for advice while I was waiting for replies. The left field terminal that I connect to doesn’t have a rubber spacer. The field terminal on bottom does. He said I can take the rubber spacer off the bottom and screw it back in and that would act as a ground, no wire needed. Is this true?

 

[Don Frelier]

Yes, it's essentially bolted to the engine which is DC-com or Ground.
But I wouldn't do it that way.

 

[RemCharger]

One of them grounds. So you're saying you want to swap the grounded terminal. That would be ok. By swapping the isolating washer.

 

[RemCharger]

Yes, it's essentially bolted to the engine which is DC-com or Ground.
But I wouldn't do it that way.

Why do you say that Don, that's the way they came.

 

[69Bee]

I see a number of issues:
1) Early single wire now a 2 wire field
2) Five diodes are gold, and 1 black (the 3 on the case should likely be black for negative)
3) is the correct field winding inside?
4) Seeing these issues, what else might be wrong?

 

[RemCharger]

Here's an original 67 for reference

 

[Don Frelier]

Why do you say that Don, that's the way they came.

See post #4

I've been running the solid state with a dual field for 25 years.
They work better.

 

[R/T Boy 67]

Çheck both field terminals for continuity to the case. If one is, then connect your field wire to the other one, and it will work. If neither is continuous then ground either one and connect the field wire to the other one.

 

[jmbass98]

Okay. Thanks for the posts, I think I understand where to go from here.

What should my line of testing be when trying to determine where the issue is with my charging issue? With a multimeter.

What should alternator read at idle / at speed? What should voltage regulator (mechanical points-style) read? Etc..

Trying to find the fail point here.

Everything is new except the alternator (which I am about to replace) - battery cable, wiring harness, and voltage regulator.

 

[jmbass98]

Also, car came with a ground cable from front-left intake manifold bolt to the radiator core support. No firewall ground. Gonna add one from back-left intake bolt to firewall, as well as a ground wire from voltage regulator case to the block to see if that makes a difference.

 

[RemCharger]

See post #4

I've been running the solid state with a dual field for 25 years.
They work better.

Ok I gotcha. Yes I have an electronic on mine to, had to roadside emergency.
I guess it depends if the OP is going for original or not.

 

[jmbass98]

I'd like to get an understanding of how to get my stock system functioning as it should before I start messing with upgrades and cutting into the existing wiring harness.

 

[Don Frelier]

First just check at the battery.
Should be around 12.5-12.7 just sitting there.
Next after starting maybe 13-13.5 (depends on the alternator, battery and how fast your idle is...)
Finally speed up the engine and it should head towards 14V
But the ammeter will tell you a lot as well.

 

[Don Frelier]

Also, car came with a ground cable from front-left intake manifold bolt to the radiator core support. No firewall ground. Gonna add one from back-left intake bolt to firewall, as well as a ground wire from voltage regulator case to the block to see if that makes a difference.

There should be an open bolt hole 3/8" on the back side of the passenger head towards the firewall.
That's the way the factory supplemental ground is connected.
Then you don't need to touch any intake bolts.

 

[Nacho-RT74]

Okay. I spoke to a alternator rebuild guy near me for advice while I was waiting for replies. The left field terminal that I connect to doesn’t have a rubber spacer. The field terminal on bottom does. He said I can take the rubber spacer off the bottom and screw it back in and that would act as a ground, no wire needed. Is this true?

View attachment 1293159

View attachment 1293160

better if use a washer to replace the isolation washer, for brush firmless.


On a side note... bend or clip off the prong you ground to save from conect accidentally there the wire coming from reg or will short out as soon you put the key in run

 

[Nacho-RT74]

Here's an original 67 for referenceView attachment 1293191View attachment 1293192

View attachment 1293190

This would be the correct alt for the OP, HOWEVER the one he got is the one used at factory for the 69/71 period, when still being roundback they become on dual field for the electronic reg system. Simply grounding one of the brushes will replicate the earlier single field wire setup for mech reg