I am working on a 1994 Dodge Ram 1500, 5.2L 4x4. It belongs to my dad. He said he tried to start it today and the battery was dead. He jumped it and drove it to a battery place and they tested the battery and told him it was not the battery. They thought it was the alternator. When I went to his house to check it out, it started right up, but the voltage gauge was pretty low, but not in the red yet. I took the truck to my house, stopping on the way to buy a new alternator. On the drive home the voltage gauge started to slip lower and lower, eventually getting to the red and making the truck run like crap...the radio and gauge lights were so dim they were almost impossible to see. Headlights were not on, this was during the day. I got home and put the new alternator in. I had to jump it because the battery was dead. Once started, I checked the voltage gauge..it was low, but not in the red. Within 5 minutes it was in the red again, so I turned the ignition off. I went out to pull the codes and I got code 12 and code 37. I know 12 if because I disconnected the battery, and code 37 is low voltage at the torque converter clutch lock up sensor, probably a symptom of this, but not the cause I assume.

Ok, so, any suggestions about what this might be? Does the ECU regulate the charging system voltage in 1994 model year? What is the black box you have to attach to the back of the alternator? Could this be bad? It is hard wired in, so I bet it is a dealer only part. What else should I check?

Thanks for any help.

 

who checked the battery?....i was having a prob with one of mine b4, walmart checked it and said good, autozone said bad

 

not sure, it belongs to my father and he took it to "the battery place" he said. I checked it with a voltmeter, so no load test. IT had 10 V, but it had been through a lot by the time I got to it.