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Thread: Alternator?

  1. #1
    Join Date
    Oct 2003
    Location
    Lacombe, Alberta
    Posts
    119

    Default Alternator?

    While driving today, my tach reading dropped to 0, but would jump intermittently. At the same time, the voltage reading dropped to about 9 volts, and stayed there. I'm assuming that it's the alternator that's Fubar, since it happened to me 2 years ago as well, but I thought I'd just touch base with all the gurus and see if it might be something else that I'm missing.
    1997 Chevy K2500 E/C Auto - K & N Filter, 3" exhaust, no cat. Midas Flowmaster muffler, Kennedy ECM, Peninsular Diesel Marine upper intake manifold, 3-gauge 'B' Pillar gauge pod, Autometer Phantom gauges, Boost, EGT, and Tranny temp. Homemade air/air intercooler setup, with puller fan. Phazer Gear timing, Fluidampr harmonic balancer, 250,000 kms.
    2009 25' Springdale 5th wheel trailer
    1978 Z28 4sp Camaro (in middle of restoring it)
    1963 Dodge 2 dr. Hdtp., Model 440 (will be a Max Wedge clone)
    1979 GL1000 (Honda Goldwing)

  2. #2
    Join Date
    Jan 2003
    Location
    Boonville, IN
    Posts
    28

    Lightbulb

    I've changed out an alternator for similar symtoms. Come to find out that is was a bad cable between the batteries. The problems would come and go. Checking voltages at idle would look OK. But after driving a bit, it would start acting up again. I found it by loading the electrical system at idle (A/C on, high beams, brake lights, ect.) I read a large voltage difference between the positve terminals of the batteries. Replaced the crossover cable and the problems were gone.
    94 K3500 Dually 4x4, Avant 18:1, Girdled, ceramic coat pistons, Phaser gear drive, 98 cooling mods, PMD cooler, JK chip, JK 4" exhaust, Gauges

  3. #3
    Join Date
    Apr 2001
    Location
    Newberg Oregon
    Posts
    12,282

    Default

    The GM system on these diesels uses the left battery to dump the alternator into.
    The problem is many times the ground cable on the left battery. If they have some time on them replace both ground cables. The problem is the eye at the engine end, they corode in the crimp and then quit working due to high resistance.
    My 94 did this and it was the reason I got the truck. The former owner had had the truck to many shops and everyone told him it was a bad computer.
    HMMMMMMMMMMMM low volt readings, wierd running and such. Replaced the grounds and Pooooof all fixed.
    Guy practically gave me the truck just to be shed of the problems.

  4. #4
    Join Date
    Jan 2006
    Location
    Louisville Kentucky
    Posts
    85

    Default

    Yep, it is all true. Mine was doing this and the alternator soon went out. Replaced the alternator, problem stopped. One of my next projects is to replace all the battery cables with Welding cables.
    1994 chevy turbo diesel 3500 4WD extended cab.
    4 inch Pinnacle exhaust from the turbo back
    Kennedy OPS harness (yet to be installed)
    FSD cooler (yet to be installed, planning on placing in fender to pick up air from intake)
    Bet top extendable mirrors.

  5. #5
    Join Date
    Mar 2000
    Location
    Ft Jackson, SC USA
    Posts
    1,073

    Default

    My factory alternator lasted to about 100K miles I bought a lifetime replacement and promptly replaced it about once a year for about four years. I finally replace all the battery cables (to include the cable from the alternator to the battery) and after that my alternator has lasted.

    Since I owned the truck I have cleaned the cables every fall, but the cables coroded up inside the cable.

    I used 1 gauge welding cable for mine.

    Carey
    97 GMC K3500 6.5TD 4.10 CC SRW +259K miles; Kennedy Fan Clutch w/ 20" steel fan; Greg's Oil Cooler Lines; Racor 445 30 micron w/ heater pre-lift pump; Dr Lee By-pass Oil Filter; High Idle Switch; Revo 265/75/R16 Load Range E tires

  6. #6
    Join Date
    Oct 2003
    Location
    Lacombe, Alberta
    Posts
    119

    Default

    Thanks for all your replies. I purchased the alternator at Napa 2 years ago in August, so it was still under warranty. We can't get a lifetime warranty from Napa here in Canada. They gave me a replacement, which has a 3 year warranty, and all seems good now. The voltage does fluctuate more than the previous alternators did, so I'll keep an eye on it, but I do have my tach reading back . Does anyone have any idea why these trucks of ours seem to eat alternators? The original alternator failed and was rebuilt in 2001, at about 75,000 miles, then it failed again in 2004, with about 130,000 miles, to be replaced with a Napa unit, and now with about 150,000 miles. That just seems excessive to me.
    1997 Chevy K2500 E/C Auto - K & N Filter, 3" exhaust, no cat. Midas Flowmaster muffler, Kennedy ECM, Peninsular Diesel Marine upper intake manifold, 3-gauge 'B' Pillar gauge pod, Autometer Phantom gauges, Boost, EGT, and Tranny temp. Homemade air/air intercooler setup, with puller fan. Phazer Gear timing, Fluidampr harmonic balancer, 250,000 kms.
    2009 25' Springdale 5th wheel trailer
    1978 Z28 4sp Camaro (in middle of restoring it)
    1963 Dodge 2 dr. Hdtp., Model 440 (will be a Max Wedge clone)
    1979 GL1000 (Honda Goldwing)

  7. #7
    Join Date
    Jan 2006
    Location
    Louisville Kentucky
    Posts
    85

    Default

    Quote Originally Posted by KallyI
    Thanks for all your replies. I purchased the alternator at Napa 2 years ago in August, so it was still under warranty. We can't get a lifetime warranty from Napa here in Canada. They gave me a replacement, which has a 3 year warranty, and all seems good now. The voltage does fluctuate more than the previous alternators did, so I'll keep an eye on it, but I do have my tach reading back . Does anyone have any idea why these trucks of ours seem to eat alternators? The original alternator failed and was rebuilt in 2001, at about 75,000 miles, then it failed again in 2004, with about 130,000 miles, to be replaced with a Napa unit, and now with about 150,000 miles. That just seems excessive to me.
    Yep, that is an interesting question as far as alternator life. I wonder if it is underhood heat? Our trucks are kind of compact with not much open air flow area.
    1994 chevy turbo diesel 3500 4WD extended cab.
    4 inch Pinnacle exhaust from the turbo back
    Kennedy OPS harness (yet to be installed)
    FSD cooler (yet to be installed, planning on placing in fender to pick up air from intake)
    Bet top extendable mirrors.

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