I have a 2005 Ram 1500 with the 5.7L engine. Yesterday, my "Check Gages" light came on. I looked over my gauges to find my battery gauge flat dead. I stopped, restarted, and the gauge sprang to life, lasted about 2 minutes and went dead. Took the truck down to Autozone, they tested it, and the alternator tested bad (volts no more than 12V, contstant pull on the battery). I got a new alternator and popped it in. The gauge kept acting funny, so I had it checked again. New alternator is acting just like the old one... no more than 12 volts, constant draw on the battery. Since the voltage regulator is built into the alternator, I cant change that as well. Cables look good. Battery is the original.

I would have expected the alternator to keep the volts up, even if the battery wasnt getting charged. The last time I got out of it, I test started it, and it is starting to sound a little sluggish on the starter.

Any ideas? Is there something else that works into charging the engine?

EDIT: I have now replaced the battery, and the problem remains. By the time I got to the battery shop, the battery was not capable of starting the engine. Also, my Air Conditioning is no longer working (clutch isnt engaging). Did I mention that I had the truck at the dealer just last week for a new transfer case and rear end rebuild? That was under warranty with 40 miles left. 100 miles later, the car's chargins system doesnt work and now the air conditioning isnt working either... and it is just outside of warranty.

 

I'm having the exact same problem. Did anyone come up with a solution for this?

 

from what i have been told, the alt is different from what you think. The regulator is not in the alt but the PCM controls it. Are you getting any CELs?

 

Nope none at all. It started acting sluggish on startup a couple weeks ago. Took it to autozone to have the battery and alternator tested, both check ok. Today it started with the battery gauge dropping to nothing and the engine shuts off.

One other thing I did notice. I started the engine and the battery gauge was low, just above the 1st mark. I turned on the air and it dropped all the way to nothing and the truck began to die. Don't know if this helps.

 

Anyone have any ideas ?

 

Sounds like the AC is stopping the belt maybe and stopping the alt. This happened to me this winter when my fan was packed full of snow and stopped the belt. If your tensioner is bitched this could cause problems. Do your hear squealing or anything?

 

I had the exact same thing happen to me Easter morning. I got the kids all loaded up and was ready to head to mom's, opened the garage door, started the truck, and nothing on the volt gauge. I got out and checked the serpentine belt and all wire connections. Got in started it again and nothing on the volt gauge. Then I disconnected the battery for 10 minutes and everything has been fine since.

 

You could always swap batteries just to make sure that is not what it is even though you were told your batt was good.

 

Looking at the wiring diagrams for my 02, the regulator is still in the alternator, but the PCM controls the rate of charge with input from the battery's temp sensor. If it thinks it's controlling the rate properly, it won't set a CEL but there won't be enough of an output voltage from the alternator to keep the battery charged.

The problems described in this thread my be related to the PCM not allowing the alternator to charge at a high enough rate (bad temp sensor?), or might be as simple as a corroded battery ground wire connection (on the engine block perhaps). Make sure all battery wire connections on all ends are clean and tight.

 

All ground wires seem to be tight with no corrosion. Well I pulled the alternator/generator off the truck and took to advanced. According to their machine it tested good. I took the battery had them charge and test it. I was told that the battery was bad so I bought a new one. I was told that the battery I had (Interstate) was bad about not showing up as bad on the portable machine used through the trucks computer. It's been on the truck for a couple weeks now and haven't had any problems starting. However, the gauge is still reading slightly lower than the halfway point and the a/c doesn't seen to be blowing as cold. I just replaced the belt so I'll see what happens now. I guess the next thing will be the belt tensionier. Nothing like throwing money at a problem till it's fixed. Thanks to all that have replied and any further info, suggestions, or even a good guess or two is appreciated.