'99 D2 Alternator Intermittently Not Charging

Maximumwarp

Maximumwarp

Well-known member
Mar 22, 2015
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26
Fairburn GA
Title pretty well sums it up, alternator is only charging when it feels like it. Started happening at Winter Romp a few weeks ago. Pulled it off the trailer and the truck was running off the battery, nothing from the alternator (I have a Scangauge hooked up and I was watching voltage on it), battery light was coming on, Amigos came on, and dash lights were dimming. Drove it for a little bit and it popped back up to 14.1 volts then behaved the rest of the weekend with no hiccups, dash was clear of all warning lights. Once back in Georgia, the girlfriend drove it and the alternator failed again on her way back from an errand, battery light on the dash on top of the M+S lights. I assumed the alternator was the culprit and had it rebuilt at a local shop. They replaced bearings, brushes, and the voltage regulator, but it doesn't appear that they re-wound it. After installation, it appeared to be throwing out sufficient charging voltage (14+), but after letting the truck run for a few minutes and get to closed-loop, it dropped back under 12, again acting like the alternator wasn't putting out any voltage. I let it sit for a while and re-started, again with the same pattern of results. No battery light on the dash when I observe the voltage drop from the 14+ to the 11.9-ish reading.

Is there something dumb I'm missing? I haven't started poking around with the voltmeter yet, but I was going to start with verifying the alternator output voltage. Since it was just re-built, I wouldn't think the alternator is the culprit, but anything is possible. I've checked the connections and all seem secure. It should be noted that right before I went to Romp I installed a new starter, but that's two wires, so I can't imagine I boogered that up. Fuses all appear intact, but since it charges correctly sometimes I didn't expect to find any blown.
 
Maximumwarp

Maximumwarp

Well-known member
Mar 22, 2015
836
26
Fairburn GA
German Gruner said:
You must check mass connections. All these 10mm nuts, specially the first, coming from battery negative cable. These pattern can damage rectifiers and regulator. Its important to solve it.

Regards
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All the connections are tight, and I don't see any obvious signs of corrosion, but I was considering taking them all off and cleaning them anyways. I just don't think that's the root problem since sometimes it charges just fine. It's not like I'm losing charge when I hit a bump or anything either. I'm observing both scenarios when the vehicle is stationary in my driveway.
 
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bovw

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Apr 1, 2006
3,128
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Orange, VA
How old is the alternator? I have an 04 D2 and a 2000 Landcruiser. 2 years ago on a trip to Idaho from VA In the Landcruiser, I had the battery light come on after fueling up in WY. It would go out if I revved the engine. I continued on reaching Idaho the next day. 2 days there with no problem. First day on the return trip it came on after fueling again, ended up getting the alternator replaced in Kimball, NE. No trouble with it since. Between the two times the battery light came on, it stayed off.
 
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DiscoHasBeen

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Aug 7, 2016
1,171
262
Indy
Maximumwarp said:
I assumed the alternator was the culprit and had it rebuilt at a local shop. They replaced bearings, brushes, and the voltage regulator, but it doesn't appear that they re-wound it.
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Well, because you cheaped out now you can't eliminate the alternator altogether. So now you throw darts at the wall....
 
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discostew

Well-known member
Sep 14, 2010
7,733
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Northern Illinois
I would pull on all the cables, move them around a little to see if you can duplicate it. The main grounds and the pos cable to the field terminal. Strange that the voltage drops right to battery voltage.
I’ve seen the brass commutator ring that the brush rides on get loose on the stator. It kind of moved a little on the stator. That one did similar shit.
 
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DiscoHasBeen

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Aug 7, 2016
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Indy
discostew said:
You know that he knows how to fix cars right?
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The guy at the local shop who rebuilt his alternator? No, I don't know if he knows how to "fix cars". My point was why didn't he just buy a quality alternator and then you wouldn't have to worry if it had been rewound or whatever.
 
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discostew

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Sep 14, 2010
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Northern Illinois
Because he decided to do it the way he did it. Some other idiot would have had to rebuild a remanufactured alternator you could buy. What the hell difference does it make. He got to see the operation that reconditioned his alternator. One you can buy was probably put together by some Chinese kindergartners for a pack of smokes.
 
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rovercanus

rovercanus

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Apr 24, 2004
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There's nothing wrong with an automotive electrical shop rebuilding an alternator. It's possible they missed on this one. Maybe they didn't replace the diodes.
 
Maximumwarp

Maximumwarp

Well-known member
Mar 22, 2015
836
26
Fairburn GA
Well this thread got interesting.

I poked around with the voltmeter and nothing seemed amiss, so I went ahead and cleaned all the connections with a wire brush and battery terminal spray, but none of them really had any appreciable corrosion. In the process of doing this, I found one of the grounds that mounts to the studs inside the right fender to not be as tight as I had originally thought. During my cursory wire wiggle test, the cable didn't feel loose (likely because it's strapped to other nearby wires), but when I went to remove the nut to clean the post and terminal, it didn't take any pressure at all from the ratchet to come loose.

So far, so good, but we'll see with further road tests. The $60 at the alternator shop still feels worth it, as the tech remarked that the stuff he replaced looked worn out. C'est la vie. Funny it behaved all through Romp. It's as if the old thing preferred getting beat on in the woods to street driving.
 
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DiscoHasBeen

Well-known member
Aug 7, 2016
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Indy
rovercanus said:
There's nothing wrong with an automotive electrical shop rebuilding an alternator. It's possible they missed on this one. Maybe they didn't replace the diodes.
Click to expand...
True that. I would rather not buy reconditioned when it comes to something electronic but even "new" can be defective I guess. That said, some things I'll cheap out on. An alternator, starter, shit like that, no.

Funny story time. I had a starter go out on a fairway mower. OEM $695. A member owned an ag fertilizer business. He employed a mechanic. Told me to take the starter by. Walk into this shop to find a beer-bellied older man in bibs with no shirt on. Takes the starter apart and tests the bendix, I think. It's been some time ago. Anyway, the following conversation went something like this.

Yeah, I can fix it.
Great, how much?
Well.... I mean.... look, it's probably going to be around $100 or a little more.
OK, well I need it so I guess I can do that.

Fix it he did.
 
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