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I recently purchased a 98 dodge ram 1500, standard transmission, 5.2L 318, 4 x 4. I've already done some work on the truck... Most everything to do with the cooling system. After replacing the water pump I had a friend tighten the negative battery cable. Since then I can't keep the battery voltage up. I've changed the batter, battery cable clamps, and alternator. The problem remains the same the voltage is wacky... Apparently a technical term as it is the parts guys word not mine. With some research I learned there are 2 different alternators for the 5.2L...90 volts and 136volts. In several places it says magnum on the engine. How do I know which alternator I need? Or if that is in fact my problem?
 

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Explain wacky. If it's jumping up and down it may be the regulator in the pcm.
I took it to autozone to have the alternator tested and both times I was told that the alternator was on its way out. It was the voltage that wasn't hitting the correct numbers. But that was with the old and new... Rebuild... Alternator. It's not putting out any codes so nothing comes up when I have it hooked up to the scanner. And my check gauges light comes on. The only gauge that is off is the battery. And it's died on me twice because my battery drained... While running.
 

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If they tested the new alternator and said it is on its way out, then they should warranty exchange it for you.
I'm not that familiar with the more modern PCM controlled vehicles, but most alternators are externally regulated. I see a reference by Moparite that the voltage regulator is in the computer. Double check that and if it is not, have the regulator tested or just outright replaced.
 

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If all they did was take voltage readings when the truck was running that's not going to cut it. Alternator could be good but the problem be else where. Check the wires coming from the alternator going to the battery (fuse in the power distribution box under the hood) and going to the pcm. Take the plugs off and look at the terminals on the plugs. Any burnt or corrodes connections need to be repaired. If you don't find anything most likely the regulator crapped out in the pcm. Then you need to replace it or put on a separate regulator.
 

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If they tested the new alternator and said it is on its way out, then they should warranty exchange it for you.
I'm not that familiar with the more modern PCM controlled vehicles, but most alternators are externally regulated. I see a reference by Moparite that the voltage regulator is in the computer. Double check that and if it is not, have the regulator tested or just outright replaced.
The voltage regulator is inside the alternator. And I didn't get the new alternator from autozone but have talked to the place I got it from and they will exchange it if that is what's wrong.
 

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If all they did was take voltage readings when the truck was running that's not going to cut it. Alternator could be good but the problem be else where. Check the wires coming from the alternator going to the battery (fuse in the power distribution box under the hood) and going to the pcm. Take the plugs off and look at the terminals on the plugs. Any burnt or corrodes connections need to be repaired. If you don't find anything most likely the regulator crapped out in the pcm. Then you need to replace it or put on a separate regulator.
I've checked wiring when I replace battery cable clamps. There was a lot of wiring for KC lights that were no longer attached to anything but the battery. So all that is gone and new clamps in place. I will check to see if any of the wires are corroded. I've checked the inside fuse box but not the one under the hood. I tried the cheaper fixes first. But it's so strange that the truck dies while running.
 

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Aftermarket stereo or OEM iv seen it before on a friend's ride they crossed +/- causing a short
After market however it was installed before I bought it. I've driven it a few times before the battery issue. I bought the truck knowing that it over heated. Changed radiator right off the bat. Used it for work a couple times then it over heated again when I was driving it. When I looked under the hood the engine was wet. So water pump, radiator fan clutch, thermostat... Which was missing entirely... And fan belt were all fixed. Friend of mine was helping and I asked him to tighten my negative battery cable clamp. It was after that that it died on me. I was driving when the check gauges light came on. Had a friend jump it but didn't get far. So he went and got his truck and we put his battery in my truck which got me home. Figured it was the alternator had it tested and was told that not completely dead but on its way because the voltage readings were super low. So alternator was purchased and put in. Went to take it for a drive. It did ok the first time but went out again and the battery lost power and the truck died. Brand new battery at this point too. So hot it to autozone. They charged the battery and changed the battery cable clamps. One of the negative wires wasn't even touching the metal clamp so fixed that. Then they testesd the alternator and again said the voltage was really low... This is where I was told the voltage was wacky. Got it home and it's been a lawn ornament since. When I went with a friend who was getting stuff for himself I was checking alternator prices and and asking about an external voltage regulator. That's when I was told that a 5.2L could have one of 2 alternators one has 90 volts and the other 136. I asked how do tell which one I need. And he shrugged said it doesn't say anywhere what voltage it is and they look identical. I wasn't wanting a project truck nor was I looking for an expensive lawn ornament. So any help is greatly appreciated.
 

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Check make sure your grounds fro motor to body / chassis are making good connection I feel u on the project and ornament thing friend of mine has bout ten of them
 

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To do a real test of the alternator you need to do a full field test. This allows the alternator to put out it's maximum so you can see if it's the alternator or something else is the issue. Long video but it walks you through the process.

 

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Which alternator do you have/need? The standard alternator is capable of generating 90 amps of current at 14 volts. This is usually sufficient to run all of your electrical accessories (radio, headlights, windshield wipers, etc) and still charge the battery at the same time. Some vehicles came with "heavy duty" alternators that are capable of producing 136 amps at 14 volts. These will overcome most high draw accessories such as KC lights, amped stereo etc. I think the HD alternator was an option or part of a package that you may not be able to find out without decoding the trim tag or finding the build sheet. It will not hurt anything except your wallet to use the higher amp alternator but more than likely the 90 amp will be sufficient for your application.

Meanwhile, warranty replace the new alternator and see if that fixes your problem. No point chasing your tail when you already know of one faulty component.
 

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Is the battery ground cable still the original? They do go bad. I've replaced two year old cables on trailer trucks that were completely shoot from corrosion pumping thru the wires. Some were so bad they had knots inside the cable jackets. Under size cables are just as bad. I was raised on the assumption that 70% of electrical issues are from bad grounds.
 
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