Hello,

My 2004 Ram 2500 5.9L Diesel is having an issue with charging.

Last Sunday I took my truck to the lake to get my boat. On the ride up everything was fine, no issues. On the way home my "check gages" light came on and I saw that my charging needle was on 8. I stopped to check fuses and all were good. I got back in the truck and started it and the needle went to the bottom of the safe zone. A couple minutes later the needle suddenly dropped to 8 again and remained there for the rest of the trip. The next day I tried to start the truck and it wouldn't start. It turned over but just wouldn't catch. I could hear the starter running down. I put the charger on the battery and left for breakfast. After breakfast I tried again, this time it started fine. The needle was above the low end of the scale and stayed there. I put a code reader on it and saw the following codes P0514 and P2509.

I let the batteries charge for 2 days and took the truck out for a ride tonight. The needle held just under the 14 for awhile then dropped to the low end of good. After about 10 minute the needle dropped back to 8 and stayed there. I put the code reader back on and got no more codes, but I did check the battery and alternator and got a warning the battery voltage was low and that the alternator was not functioning. I'm going to try again after things cool for awhile and do the alternator test again when the needle is reading something other than 8.

Based on what I've googled it could be the batteries, the alternator, the PCM, the grid heater failed on, or the battery temperature sensor.

Other than testing when the needle is reading above 8, what other things should I look for? I can see if the battery temp sensor is reading wrong it could shut off the alternator. I'm hoping it isn't the PCM.

Cheers
-Bob

 

Sounds like the alternator s going. Read the output voltage, at the alternator field circuit. If that's good read it at the batteries. Depending on battery age, may want to replace.

 

Batteries are 11 years old so they could be bad, I'm willing to replace them if that will correct the problem. I'm planning on doing a load test on the batteries, just haven't had time yet.

Cheers
-Bob

 

At 11 years old. I would just replace them. Then check the charging system. Alternator has to work harder to charge a junk battery.

 

It will probably come to that. I hesitate to replace batteries, I have a really, really good history with getting amazing life out of batteries. I got 17 years out of my first Miata battery and 10 years out of my second. My boat batteries are 8 years old and still load test well. My Honda motorcycle battery is 12 years old as is my Honda scooter battery and my trolling motor battery it 10 years old and still load tests well. My Harley battery is 6 years old and that on may be close to needing replacement.

Still, I'll load test them when I get a chance and we'll see.

Cheers
-Bob

 

I've never gotten more than two seasons out of trolling motor batteries back when I tournament bass fished almost every weekend. Although I usually get 10 years out of a vehicle battery...

 

You must be doing something right...lol Anything over 2 yrs. on ANY motorcycle battery is saying something !

 

I have a 10 bank battery tender I put all my batteries on when they're not being used. I have no affiliation with them, but I've been using them for over a decade and they do a really good job at keeping a battery properly charged. I'm also old school, so any batteries with caps I check with a hydrometer and fill with distilled water when they need it. My trolling motor battery was nearly empty this spring, I had it on a different charger beside the battery tender and it has a tendency to over charge, I use it to provide 12 volt house power to my work bench. Anyway it took nearly a gallon of distilled water it was so dry. After charging after the fill I had 2 dead cells. Over the summer I kept equalizing it and keeping the water up and I was able to bring it back. I show 6 good cells now. I load tested it and it comes up marginal so next summer I may have to replace anyway, but it'll power the stereo in my workshop this winter.

Cheers
-Bob

 

I just load tested both batteries using a Schumaker BT-100 load tester. The driver's side battery tested a bit low. If it had been an 800 CCA battery it would have been marginal, but as it's an 850 CCA battery and the needle was on the line between the green and yellow at the 800 level I'd say it's a bit weak. The passenger side battery was excellent. I load tested it for 10 seconds and it still read strong. I gave it another 5 seconds and there was no change. So, I'm satisfied that one battery should be replaced but the other is still good. However even the bad battery isn't bad enough to be a problem.

I then started the truck and read the meter for charging and it showed nothing more than battery voltage. So, now I have to isolate whether it's a cable, the alternator or the PCM.

Cheers
-Bob

 

Just got done and everything is good now. After checking the batteries and the cables I came to the conclusion that it's the ECM or the Alternator. I removed the alternator and took it to Auto Zone. They put it on their bench tester and it failed immediately. We grabbed a new one off the shelf and tested that one and it passed all tests. I installed it and ran through a number of diags and everything is working perfectly.

As for the batteries as I was removing the cables to replace the alternator I saw a tag that said they're 750 CCA which is less than I thought. However, that means both batteries are good enough to get me through the winter. My drivers side battery may be on the low side of good, but it's still good.

So, it's all a happy ending. The truck is fixed and I was able to put into tools (battery tester and code reader) what it would have cost to have someone else do this for me.

Cheers
-Bob