2003 Ram 2500 starting problem

2003 Dodge Ram 2500, 5.7L Hemi.
Two weeks ago truck would not start. All electrical dead. Not even the key fob worked. (Was a bitch as the wife and boy were picking me up
from a 3-day stay in the hospital. Had to fold my 6'5" frame with a broken leg into her little skateboard Volkswagen for the 50 mile trip home. Not fun.)
Truck would start when jumped from another vehicle, but the battery would not hold a charge. restarting was hit & miss.
Towed it to my mechanic, who made the following tests and repairs: Check charging system 14.29 regulator volts, diode pattern is good, 124 peak amps, battery test good and recharged. Let sit for a few days, retested charging system, battery failed test. Recommend replacing battery.
So I authorized a new battery even though the old one was less than a year old (sometimes you get a bad one). Truck started fine at first.
A few days later I had the same problem. No electric at all. Truck would not start. Same symptoms. Would start when jumped but could not restart after jump disconnect.
Towed it back to my mechanic yesterday.
Clearly it's not the battery. It's something else. A short in the charging system? Bad alternator?
Can anything else be causing this problem?
FWIW, my mechanic is a good one. Worked with him for years and he's never done me wrong. But I feel he should have a better handle on this problem than what he's done so far.
Frank
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On 9/5/2012 10:27 AM, Frank Warner wrote:

I would strongly suggest that you go to http://dodgeforum.com and post your question in the appropriate forum.
Don
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On 9/5/2012 11:27 AM, Frank Warner wrote:

Nothing is clear, a battery could be bad from the box. It happens, happened to me last year.
But, I'd suggest a secondary volt meter temporarily attached directly to the battery. Monitor this and see if the 'charge' voltage (that 13.7-14.7 volts while running) goes away or not.
Some things to consider:
Are the lights as bright as they should be all the time? Or do sometimes they go dim?
Did the mechanic check the cables at both ends (especially the ground cable?) Did he check voltage at the battery posts (not the cable clamps, but the posts themselves) to confirm the battery was truly dead?
It is very unusual for a battery to go totally dead (no voltage) unless there is a parasitic draw running it down. You may also want to run a proper parasitic draw test. It is definitely possible that something is running the battery dead despite the vehicle being turned off.
And, BTW, this is the right forum for your question, even if someone says otherwise.
I strongly suspect a parasitic draw is draining the battery, though perhaps it could be the cable(s).
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Look for a parasitic load. Something draining the battery that is a somewhat low current drain but big enough to kill the battery.
Two I've seen more often than not is a glove box light that does not turn off. Same for an under hood light.
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I have noticed that little things like the cigarette lighter or the window lock/unlock buttons stop working several days before the event. Could one of these or something similar cause a parasitic load?
Frank
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On 9/6/2012 8:13 AM, Frank Warner wrote:

It easily could be related. Much of this stuff is controlled by the BCM or other computers in this truck, and the computer could be commanding a load at the wrong time.
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wrote:

The mechanic is checking those things. He agrees it's not the battery or charging system, and that there's a draw somewhere draining the battery while the truck sits. He's tracing the harness and checking the modules to find out where the draw is coming from.
Thanks for everybody's help. I'll try to keep the group posted if we find the problem.
Frank
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With the ignition off remove the + terminal from the battery. Then place a VOM amp meter (10 amp range should be enough) between the battery+ and the hot lead to the rest of the electrical system.
While doing this make sure the doors are closed and that you don't open the doors while testing as you can get an over current on the meter. (some meters are over current tolerant but the cheap ones (~$20) will blow a fuse and fuses while cheap are often hard to find.)
Best to use a clamp on DC current meter if you have one but those are not cheap.
The process I use is to disconnect the various electronics one at a time until I find the bad boy. I would mention that car alarms especially aftermarket units and wireless key switches are a popular problem.
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Would add that once the load is determined switch the current range of the meter to a lower scale as you seach out the problem.
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Frank Warner wrote:

Check the battery terminals. Check the voltage at the battery posts then check the voltage at the clamps.
You should also do this check when trying to start. If the voltage drops at the clamps when starting the clamps are bad.
You can put a shim between the post and clamp for a temporary fix.
JAM
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