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6.5L Turbo Diesel 1992-00 6.5TD - Discussion forum for the 6.5L engine.

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  #1  
Old 06-02-2006, 10:21 PM
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KallyI KallyI is offline
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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.
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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)
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  #2  
Old 06-03-2006, 12:02 AM
gerry1 gerry1 is offline
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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.
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Old 06-03-2006, 08:52 AM
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Robyn Robyn is offline
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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.
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Old 06-04-2006, 02:17 PM
signgrafix signgrafix is offline
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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.
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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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Old 06-04-2006, 03:32 PM
CareyWeber CareyWeber is offline
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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
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Old 06-05-2006, 06:20 PM
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KallyI KallyI is offline
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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.
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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)
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  #7  
Old 06-05-2006, 09:45 PM
signgrafix signgrafix is offline
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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.
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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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