Charging system troubles - Dodge Diesel

MDLP412 · 10-30-2008, 10:26 AM

my uncle has a 01 automatic that i put a new lift pump on for him, on the way back to deliver his truck to him the "check gauges" light came on. i checked and the voltage was down to below 8V so i took the alternator off and it tested bad, after i put the new one on i started the truck and it hung around 10-11ish for about 3-4 min and then it dropped right down to below 8 again. had the new alternator tested and it tested good, i was also told the the voltage regulator was in the PCM (JTEC) and it might be a bad computer. does this sound right to anyone or has anyone had the same problem? any info would be helpful. THANKS!

Grider Pirate · 10-30-2008, 08:31 PM

As a starting point, I would disconnect both batteries, check voltage while disconnected, and charge them before spending any more money. After charging, check the voltage before reconnecting them. If either is under 12.6 volts, it's likely bad, and troubleshooting charging problems with a bad battery is tough.

dozer12216 · 10-31-2008, 06:44 AM

Yes, check both batteries separatelly.
A quick test of elecrtonics for charging is with engine running, the alt pulley should be a magnet. The reason. IF PCM is working regulator circuit the rotor will be a magnet and the alt pulley is also a magnet. Carefully hold a screwdriver near front of pulley and should pull to pulley.
A FSM would help clear the issues of testing.

mini14 · 11-02-2008, 10:30 AM

yes, pcm controls voltage regulation, many have had your prob. u can bypass the pcm control and add an external voltage regulator.use the search function on this board and subject u will find what u need.

10-30-2008, 08:31 PM	#2
Grider Pirate Registered User Join Date: Nov 2006 Location: Las Vegas, NV Posts: 189 My Photo Gallery My Classified Ads	As a starting point, I would disconnect both batteries, check voltage while disconnected, and charge them before spending any more money. After charging, check the voltage before reconnecting them. If either is under 12.6 volts, it's likely bad, and troubleshooting charging problems with a bad battery is tough. __________________ Grider Pirate, USAF RET '99 2WD, Auto trans, 215,000 miles, DSS, New VP44, new LP, cheap DIY low fuel press. warning light. '01 4WD, 175,000 miles. Dyna mat throughout interior, Alpine Stereo with remote amp, '03 track bar, Bilsteins, '08 (17") Wheels, 1 Ton chevy wheel cylinders, FASS, ATS trans, 3.74 gears, BHAF, 3 piece exhaust manifold, Banks power elbow, 4" exhaust, Banks High Ram intake, Stage 1.5 F-1 injectors. Janus C glider Grob 104 glider

10-31-2008, 06:44 AM	#3
dozer12216 Registered User Join Date: Dec 2007 Location: North Carolina or Kentucky. Take your pick Posts: 2,716 My Photo Gallery My Classified Ads	Yes, check both batteries separatelly. A quick test of elecrtonics for charging is with engine running, the alt pulley should be a magnet. The reason. IF PCM is working regulator circuit the rotor will be a magnet and the alt pulley is also a magnet. Carefully hold a screwdriver near front of pulley and should pull to pulley. A FSM would help clear the issues of testing. __________________ 2008 1/2 3500 dually that is stock except for 2 micro inline filter for fuel. Infero red extended cab, long box made for highway towing.

11-02-2008, 10:30 AM	#4
mini14 Registered User Join Date: Feb 2005 Location: New York Posts: 1,014 My Photo Gallery My Classified Ads	yes, pcm controls voltage regulation, many have had your prob. u can bypass the pcm control and add an external voltage regulator.use the search function on this board and subject u will find what u need. __________________ 99 auto 4x4 4.10 rear,no s ring,bhaf, edge ez, 4" s.s. magnaflow 05 Q.C. auto, stock....for now...

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