Hey there fellas! I got a 94 dodge ram 2500 5.9L gas 4x4 with some power issues that started recently. At first when driving and at a red light the power gauge would go down from 14 to about 10, and all the lights would dim. My 1st thought was the alternator. I took it down to AutoZone and had it tested they said one of the 2 batteries wasn't any good. I took them both out and left them to charge. One tested fine but they told me the other was good but on its way out, cuz it was having a hard time taking a charge. Went ahead and replaced both batteries and the alternator. No change. Went to pep boys and had it tested. They said my new alternator was putting out zero volts and was no good. Took it out again and took it to o Reilly's they agreed the alternator was no good. Got another one and put it in and still no change. When it starts and i take the jumper cables off it clicks and everything goes dim and then dies. Please help

 

Two batteries in a truck with a gas motor??

Does the alternator charge at all?? How was it tested? On the truck, or on their testing machine?

 

yes two batteries on a gas motor, but they don't seem to be linked. I think it was mainly for a previously installed stereo Because when one has no charge left, i can switch them and I'm back to maybe 12 on the dummy gauge instrument panel. I am not sure if the new alternator (#2) is putting out anything, i haven't figured out how to test that. When they tested the other new alternator (#1), it was test both on and off the truck. On the the truck at pep boys and off at o Reilly. Im sorry I've never messed with the electrical system in a vehicle so as far as learning im at square#1. I hope y'all can be patient and i appreciate your help!

 

Trace the positive wire coming off the batteries and see where they go. Also you have a fuse in the fuse block under the hood next to the factory battery location. All power from the alternator goes to the fuse first so if the fuse is bad it will show no output on the gauge.

 

Where did he mount the second battery?

 

on the opposite side on the passenger side

 

Even though it seriously pains me to do this, I am taking her to the mechanic tomorrow. I dont have the strength or energy to deal with tracing wires down. . My OCD and stubborn ways are streaming at me right now but i just can't do it right now.

 

I hope you aren't buying new alternators to replace bad new alternators. That's what warranties are for. I've seen multiple units in a rebuild batch be bad. If you don't have one already, get yourself a good digital volt/ohm meter. These are just handy to have. Don't unhook the battery while the engine is running. This is an old tale to tell if the alternator is good. It's to check if a GENERATOR is good. Chrysler hasn't used generators since back around 1961 or '62 on passenger vehicles. Alternators require an electric charge to make an electrical field where generators have permanent magnets.

The only gassers I've ever seen with two batteries were RV's. These have isolators and switches to charge the batteries.If you go to a mechanic, they may find something simple like a bad connection. I think you mentioned in your first post about this puppy it was neglected. When you find the problem, it may be something simple, just a stinker to track down. I had a Furd Powerstroke that died and wouldn't start. My neighbor is a diesel mechanic and he has tools that make me drool. All we could figure out was a bad wire somewhere. I took it to a really good, but not cheap, auto electric repair shop. It took them 3 hours to track down the issue. 3 minutes to fix it. The truck originally sold in California so it had California emissions. A kid here in Indiana put a Federal power chip in it. The computer and chip didn't play well together. They unplugged the chip and everything worked. So, it may gall you to take it top a mechanic, but in the long run, you'll be happier.

 

Her truck is obviously more than 'slightly' modified, wouldn't surprise me if the previous owner installed the second battery. Just grab the stuff from a diesel, and there ya go. Battery isolator would be a good addition though.

 

Dag dabit! There was a inverter connected between the alternator and the 2nd battery. That went out so they just bypassed it. Problem fixed. The mechanic was even stumped for a little bit, because it was charging but just not at idle. Lesson learned. Damn I hate paying someone to do something I'm fully capable of doing.