Alternator question M1009

[CSandoz]

Hello all.
I'm currently taking my time breathing new life into a 1984 M1009. It has been mostly untouched. No wire nests or hack jobs. That also means it hasn't been maintained. Go figure.

I'm tracing a parasitic draw somewhere in the system. Alternators are definitely charging. The batteries are brand new.

Naturally I start going through the TM's and start reading the stickies.

At the top of this forum I read an alternator testing post, and on the first direction at the bottom, mentioned that the driver's side alternator may not be grounded at the stud. That the mounting bolt would be the ground.

I'm a bit confused by that. I was under the impression that both alternators were not only the same but both isolated ground. In what configuration would the driver's side alternator be different?

 

[WWRD99]

Hello all.
I'm currently taking my time breathing new life into a 1984 M1009. It has been mostly untouched. No wire nests or hack jobs. That also means it hasn't been maintained. Go figure.

I'm tracing a parasitic draw somewhere in the system. Alternators are definitely charging. The batteries are brand new.

Naturally I start going through the TM's and start reading the stickies.

At the top of this forum I read an alternator testing post, and on the first direction at the bottom, mentioned that the driver's side alternator may not be grounded at the stud. That the mounting bolt would be the ground.

I'm a bit confused by that. I was under the impression that both alternators were not only the same but both isolated ground. In what configuration would the driver's side alternator be different?

That stuff does get confusing...really if your alternators are charging as they should be then the drivers side is grounded correctly...there's a stud on the back of that one that usually has a wire running to a stud by the thermostat housing...the passengers side does not. As far as a draw goes how much do you have? These things are kinda touchy on charging sometimes...Are both charging lights on the dash come on with the key and turn off once running? What's the voltage on the batteries when it is running?

 

[CSandoz]

Both of my alternators are charging. The voltage on the batteries while charging is over 14.5.
The gen 1&2 lights operate properly on key on. Gen 1 stays on untill I giver her a little throttle. Then promptly goes out and doesn't come back on. The other day my amp meter died on me so I'm waiting on new resistors for that repair. Lol

If I understand correctly, and I may not, then a simple continuity test between the grounding stud and the alternator case should tell if the isolated ground is in working order. Right? There should be no continuity between them. And if there is then something is amiss in the alternator. Am I understanding that correctly? That should stand for both alternators if they are the same.

 

[WWRD99]

Both of my alternators are charging. The voltage on the batteries while charging is over 14.5.
The gen 1&2 lights operate properly on key on. Gen 1 stays on untill I giver her a little throttle. Then promptly goes out and doesn't come back on. The other day my amp meter died on me so I'm waiting on new resistors for that repair. Lol

If I understand correctly, and I may not, then a simple continuity test between the grounding stud and the alternator case should tell if the isolated ground is in working order. Right? There should be no continuity between them. And if there is then something is amiss in the alternator. Am I understanding that correctly? That should stand for both alternators if they are the same.

Yes that sounds right, they are gounded internally. So you think you have 29 or so total volts? If you think the alternantors are your draw you can unplug the regulator as they can be the draw...but that's a shot in the dark yet...what's the volt draw that you have that's draining the battteries? Gotta be a big one unless this sits....just a cold start with the glow plugs can eat up a good bit of the batteries...takes a several miles of driving to top them off since the alts don't put out to much at idle to charge big batteries.

 

[CSandoz]

If the weather cooperates with me I'll poke around some more this weekend and report back.