M1009 Gen 1 issues- im confused

I checked voltage not running,12.2 volts each, running 14.4 volts each. No gen lights or voltmeter? Could a previous owner modified something to bypass the lights and gauge? The passenger side alt doesn’t look like it has any insulators on the mounts and yes I have a 24 volt starter.

johnjr said:

Could a previous owner modified something to bypass the lights and gauge?

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That seems to be the most likely explanation. 14.4 is a happy alternator. You don't have a charging problem.

Did you check voltage from the rear battery + post to ground? Can you post some pics?

I will get pictures when it stops raining

I had that same problem. Did you check for voltage at the voltmeter harness? My voltmeter was not working but a new resistor fixed it because it was getting voltage. Cleaning contacts everywhere and a new bulb socket resolved the get 1 light issue for me.

No, I didn’t check voltage at harness,where is the resistor you speak of? Thanks

This is a picture I received from a fellow that has charging problems on an M1009. He said he has the Gen 1 grounded. I told him this does NOT constitute an isolated ground. This will create charging issues. Am I correct on that?

Gen 1 needs to be grounded.

johnjr said:

No, I didn’t check voltage at harness,where is the resistor you speak of? Thanks

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It's on the back of the voltmeter.

doghead said:

Gen 1 needs to be grounded.

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Yes I know that. But NOT on the case. All mine are attached to an isolated ground on the back. Unless I am missing something. Anyone?

These are the alternators I removed from my M1028 and I replaced them just to replace them. I wired them just like they were and looked up the diagram/schematic and think I done it correctly. If I were to do it this way they worked as designed. If I took the time to attach the ground this way I would be wasting my time. The alternator is already grounded to the engine at 3 places. I guess I question why the isolated ground and still going to ground but that is how they were and worked so I just wire them the same way. it must have something o do with the 12/24 wiring/charging system. It just always worked from new so I just put it back together as it was. I replaced the alternators because I did not know how old they were so I wanted to freshen up a few things. I changed the starter also just as a PM. Happy New Year. It's the only vehicle I currently own and I need it 100% reliable. Hoping for that to change here in a few weeks when my new truck arrives.

cucvrus said:

View attachment 752032This is a picture I received from a fellow that has charging problems on an M1009. He said he has the Gen 1 grounded. I told him this does NOT constitute an isolated ground. This will create charging issues. Am I correct on that?

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This picture does not show if the alternator has an isolated ground(the stud location is not in the picture).

If it is not an isolated ground alternator, then it does not matter if the black wire is attached to the case.

If it is an isolated ground alternator, then it is grounded improperly(and should not work).

doghead said:

This picture does not show if the alternator has an isolated ground(the stud location is not in the picture).

If it is not an isolated ground alternator, then it does not matter if the black wire is attached to the case.

If it is an isolated ground alternator, then it is grounded improperly(and should not work).

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Exactly. My point. He bought an alternator at Autozone and installed it. When it didn't work he removed both alternators and took them back to Autozone and they tested them. They both charged 14.4 volts so he went back and installed them. I am trying to help a Man from afar.(Chicago) If it were here I could fix the issue with a minimum of questions and issues. I told him That the alternator (Gen 1) needed to be hooked up like this picture above. In my mind I don't understand how it works but it works this way so I hook it up this way. I install parts on trucks at work and follow the instructions most things are simple as that. They work when done and I don't need to know how or why. Just that they work. My question is does that isolated ground and that small wire going into the harness have anything to do with the system working correctly? If not the ground serves no purpose and the alternator is grounded via the adjustment bolt and mounting bolts. And NO it does not have a second isolated ground stud on his Gen 1 alternator. Am I asking a question out of line here?

A non isolated alternator used in the gen 1 position does not need to use the original ground wire.

It will work with or without it connected(the non isolated alt).

A non isolated alternator can not be used on the passenger side(gen 2) position.

So what you are saying is I do NOT need the ground wire on Gen 1 from the isolated stud to block and the little black wire does not need to be grounded to the stud either?

https://youtu.be/u1TV8y4iOUs
He sent me this video and said this helped him resolve the issue. Not 100% accurate but understandable. Any comments?

cucvrus said:

So what you are saying is I do NOT need the ground wire on Gen 1 from the isolated stud to block and the little black wire does not need to be grounded to the stud either?

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Your statement confuses me. You said" I do not need to..."
I thought we were talking about someone else you are trying to help. And you posted pics that I thought were someone else's.

With the correct original alternators, you do need to ground the isolated ground stud on gen 1.

This is the only picture I had other of the other guys alternator. I knew that was not considered the isolated ground and that it was wired incorrectly. I was showing you what other people think when you tell them they need an isolated ground. That was away from the other ground so to some that means isolated. I would never do that type of wiring even if it were the correct place to mount the ground. I have the situation at bay. I was sharing this and double checking because he made a valid point. If he grounds it there grounds it mounting it or on the stud it is grounded either way. I emphasized isolated ground. And he was not understanding. I am as confused as you about the whole thing. But I have it under control. It is hard to explain to someone that keeps questioning you on what an isolated ground is. I don't understand the electrical configuration. therefore I just wire it the way it was wired from new and it has worked for me for over 23 years. I am out of issues with the charging. We think we have it covered now.

Sir Richard, that was massively confusing.

I understand now. I went and looked at my truck with a test light. I also understand why they done it. It was done for 1 size fits all reasons. That was why I was massively confused. I have learned the way of the Jedi. I will continue to be vigilant and learn. I just never thought about it that much and reassembled as I took it apart. I do fully understand now. Gen 1 is fine with no isolated ground. But it cannot serve in Gen 2 location. Got it. Now off to get some bar oil for cutting wood. Happy New Year.