I just bought a 95 dakota 5.2/auto 4x4, with 122,000 miles and has been sitting in my neighbors driveway for about 2 years. I bought it from the 2nd owner. Anyway, it has very low volts. I put a new battery in it when i bought it, drove it for 1 day and that night on the way home it died on me outside my house. It started right back up and I drove it into my driveway again. Then it died again.

I replaced the alternator in it last year for the PO, but i got it tested anyway and it tested good. So I tested grounds for continuity and they look good(replaced the one for the battery, still no change), and I checked under the fuse box for a bad splice but they all seem good. When I tested for voltage at the 2 studs on the back of the alternator they test the same voltage as the battery. So I did a little research and found that the voltage regulator is inside the ECU, so I bit the bullet and purchased a new ECU, still no change. Also replaced the battery terminals and no change.

If I leave jumper cables on it it will run about 12.75-13 volts, until I take them off. Then it falls all the way too 8.. Im starting to run out of ideas, is there anything I forgot to check, or am over looking?

 

Maybe a bad battery? Have you tried charging it up and then unhooking the cables overnight and come back in the morning to see if it was still up?

But also sounds like a PCM failure to me...hmmm

 

I bought the battery a week before I started driving the truck, and would start it periodicly, and it always fired right up.

I know I thought it was for sure the voltage regulator, but it appears not. unless I got a new PCM with a bad regulator.. But I doubt it

 

Yes this sounds like good advice. Charge her up and then start diagnostics. If it still puts out 8 volts while running then you have a bad battery. An engine can run on a strong battery with a dead or no alternator for a good 30mins or more and still be only at 9-10 volts.

The autostore tests on the alternator are not always accurate. I suggest replacing it anyway. Or you have bad wiring to the PCM from the alternator.

 

ok ill try charging the battery tonight, Im pretty sure that battery is good bc i drove it all day with no problems the other day, but im down to try anything at this point.

I was thinking the same thing about the alternator so im gunna take it to a local rebuild shop and have them look at it, they always do good work so it seems better than chancing buying a new one. I put the jumper cables on it for about a half hour last night and when i took them off it immediatly started to fall off.

Im gunna do a voltage drop test today, and try to attatch the drk green wire behind the alternator to ground, well see what happens. Thanks for the quick responses much appreciated guys!

 

you sure you dont have anything on when you turn the vehicle off? I had an old chevy that stumped me till i figured out my cab lights never went off, the switch the gets hit by the door when it closes was bad. It would always drain the battery down quick for me atleast.

 

no battery drain problems, just went to start it and it almost turned over, so i put cables on it with the other vehicle off and it fired right up.

I did a quick voltage drop test that i saw online, It said start motor and turn on everything you can(lights, wipers, radio etc.) and put the positive terminal on the neg. battery post, and neg connector to the alternator case and it should read under 0.5DCV, and I got over 9DCV... So according to the video I have a bad ground somewhere. It also said put the neg. connector on the pos. battery post, and place the pos. connector to power on the back of the alternator and should have under 0.5 DCV and I got about 0.48DCV. So I dont have resistance in voltage.

So I think its a bad ground somewhere even though I think Ive tested all of them, but ill keep checking them. Did I perform the test right? Im fairly new to wiring but ive been doing alot of testing on my LT1 swap in my camaro so im becoming pretty familiar with testing them.

 

I don't know how the test goes, maybe someone else does who will chime in. If you think it's a bad ground, my not run the negative cable from the batter to a clean spot on the engine which should ground it.

 

I replaced the ground from the battery, but I ran it to the same location as it was before on the acc. bracket. Is that not a good ground spot?

 

That's a good one, my instinct is telling me it's the battery or PCM.