2nd Gen Non-Engine/Transmission Intermittent charging problem?

[CConley]

I have a 2001 3500 4x4 cummins 6 speed HO truck with 160k. Occasionally the "check instrument" light comes on and alternator gauge shows no charging. It will either start charging again on it's own, or, if I shut the truck off and restart it, everything is fine. The batteries are less than a year old. I'm assuming the alternator is working correctly, since an internal intermittent alternator problem seems unlikely. It would also seem that the voltage regulator is working correctly, since the gauge normally shows between 12 and 14 volts. Has anyone experienced this issue? Thank you, Chris

 

[WilsonF]

My 96 was that way, "on again off again" it finely went out. Turn out the diode pack in the alt. burned out. If you find that it is the alt. Have it rebuilt, don't turn it in for a core.

Floyd

 

[HHhuntitall]

Just off the info above, I'd say Alternator or PCM. Maybe a wire breakage inline to the alternator fields.

 

[Schumacher]

MY '01 did the same thing. It was the wires that plugs into the back of the alt. I had a friend watch the gauge as I moved the wires. The break was about an inch from the plug.

 

[Moe]

My 2000 did the exact same thing. Dealer checked it out and nothing found. Did store p1682 which dealer cleared. Still working.

 

[CConley]

I rebuilt the alternator with original denso parts, both bearings and brushes. The reputable shop I got the parts from said they rarely see diode issues with this alternator, and that it wouldn't be intermittent if it had bad diodes. I'll check the wiring for breakage, but I'm doubtful this is the problem. When the truck stops charging, usually at night with the additional lighting load, I can shut it off and restart, and it will charge normally. I'm going to call the shop again and double check that the diode issue wouldn't be intermittent. The truck has a 1682 code that I'll need to look up.

 

[CCiatteo]

I recently had an intermittent problem, very similar to this situation. Originally looked at crank sensor (engine speed sensor), tried adjusting it, cleaning it. Worked for a short time, or so I thought. The problem then returned, so I ordered a new one from Cummins, installed it and was OK for about a week, problem returned but was getting worse. Except now the alternator was dropping out much more frequently, but I started to notice that rough patches of road would usually coincide with the symptoms.



After having the batteries load tested to rule out a battery issue, the alternator tested to rule out diode pack, I tore into the wiring harness. Sure enough I was able to isolate a weak/broken wire in the main engine harness. The break is in the area of the main harness as it passes the fuel filter before it heads up and along the firewall over to the PCM. So if everything else is coming up good, I would take a look at the wiring harness especially if you have a lot of miles. I am sure the all the engine vibrations, combined with heat, and lowest bid on supplying the factory harness all are contributing factors.



Good luck.

 

[CConley]

I replaced the diodes (rectifier) with a heavy duty unit. The problem went away. No more 1682 (low voltage) code. In hind sight, I think the diode pack had some issue for some time , resulting in low voltage, and finally got so bad as to trigger the low voltage code. The thing that still puzzles me, is that when the check gauge light came, and the truck stopped charging (as it did repeatedly), turning it off and restarting it would enable the charging system to function, albeit at low voltage. The good news is that the original alternator made it to 160k, that it's completely rebuilt, and I understand how to disassemble and replace all the wear components. Thanks to everyone for your help. Once again my TDR subscription pays for its self ten fold. Chris