To start off with, I suck horribly at tracking down and diagnosing electrical problems - besides a total lack of patience, my color vision isn't very good (red/green color deficiency), so it's kinda hard to tell some of the wires apart.

I left my truck sitting at work since Sunday - been driving the department Cherokee for the week (hey, might as well save fuel costs when I can) - and the battery was deader than a $#!+ bug when I tried to leave today. Had to hook up jumper cables up to two cars to turn the Cummins over...one wouldn't even get the starter to click.

After driving across town (~45 minutes), I stopped at my friend's transmission shop. One of his guys started checking things out and there is a current draw with the ignition off - it's the circuit that controls the dome and cargo lights, and apparently the Chrysler EVS alarm system as well. Pulling the fuse stops the current draw, and when the fuse is replaced the alarm "chirps" and the electric door locks unlock. The wiring near the dome and cargo lights appears to be in good shape - no frays, burns, etc. After jumping the truck again - appears the battery is fried (nice sulfur smell when charging it, all but one of the cells bubbling) - I brought the truck home and disconnected all the plugs I could find for the alarm system, and everything else under the dash I could get to, but the current draw is still there.

I'm not sure how long the problem has been there - the truck normally doesn't sit for more than a day or two, which probably isn't long enough to drain the battery. When I went camping a few weeks ago, the truck sat for a little over three days and fired up fine, even thought it was cold enough to kick the grid heaters on. The camper battery may have helped "boost" the main battery a little, but it was pretty weak by then (wouldn't even fire the ignitor for the furnace), so it probably didn't do much - if anything - to help, so I kind of think this is a fairly recent issue.

So, seeing how I'm about worthless at diagnosing electrical problems, anyone have any suggestions on what may be wrong or where to go from here? I hate to pay someone to fix it - mainly because I can't afford to - so any help is greatly appreciated.

 

I did a little further "investigating" and noticed something: Besides the alarm apparently being affected by the #15 fuse, the radio and clock memory is on that circuit as well. Hmm...might have to disconnect the stereo and alarm and see if the current draw goes away.

Forgot to add, the charger is pulsing every few seconds. According to the manual that came with the charger, the pulsing means "The battery is connected to application that draws a small current (such as an interior light)."

I'm pretty sure the battery has taken a terminal dump - even with the battery alone hooked up to the charger it's pulsing. I'm hoping - seriously hoping - that it's just the battery and nothing more. Quick, somebody distract Mr. Murphy for the next day or two, I could really use a little good luck here.

 

Maybe take your bulbs out and see if the draw is there. My harness to dome and hood lights was cut by the previous owner. I suspected the same reason.

 

I tracked down the current draw to the stereo, which I don't think is enough to be a problem - wish I knew how to measure the current draw. I'm now convinced the battery was weak and just picked this time to die completely.

If I can get the truck started this morning I'll check and see what the alternator is putting out - hopefully its not overcharging and that wiped the battery out.....

 

Most radios will draw a minute amount of current with the ignition switch off. So will any vehicle with a computer. As will the clock. However, even with these current draws added together the amperage is still minute and should not drain your battery even after weeks of not starting.
To measure the drain with the ignition switch off, reconnect anything you have disconnected in your search. Get a DC amp meter of some sort. Even a VOM that will measure up to 10 amps should be OK. Disconnect both batteries. Leave one connected to ground. Set the VOM on the DC amp scale and place one probe on the positive pole of the battery connected to ground. Place the other probe on the disconnected positive terminal, thus completing the connection between the battery and the rest of the truck. Read the current draw. (amps) It should be less than one amp, but post what you find and lets go from there. Before you check the amps also set the VOM to the DC volts scale and check the battery voltage and also let us know what that is with the engine off.

 

Using my digital volt meter - which as a DCmA scale (ranging from 2 to 200), nothing is registering at all doing what you described. So, either I'm doing something wrong or the current draw is too low for my meter to read.

Had the battery charging all night, unhooked the charger for about 15 minutes and it's showing 12.09 volts.

 

If the meter is not reading anything there is no problem, but then why did those other guys tell you that they detected a current draw? On some VOM's to measure amps it is necessary to move one probe on the meter to a different place. Did you do that? Another thing you can check is to reverse the probes when doing the test and see if that makes a difference.
To verify that you are doing the test right let me put it another way. The electrical circuit for this test is as follows: the power should go from the ground wire, thru the battery, thru your amp meter and then into the truck wiring via the disconnected positive terminal. Is this the way you did the test?
Have to go out for a while but will check if you have posted anything else when I get back.

 

Thanks - I checked it the way you describe and it's still not showing on the meter, so I don't think it's enough to show or be concerned about. The tech at the shop just used a test light between the battery and ground cable to detect the current draw. The light goes out when I unplug the stereo, so that seems to be where whatever draw is going. As far as I know of, I have the VOM connected properly - one to the plug marked "mA" and the other to "COM." Tried it on all three settings (2, 20, 200 DCmA), reversed terminals, still no reading.

Coudn't get the truck to start, so I pulled the battery and took it back to where I bought it. A quick check with the hydrometer confirmed the battery was DOA. Unfortunately, since it's a commercial battery there is no free replacement period, but $43 was a heckuva lot better than some of the other alternatives.

Thanks again!

 

Glad to hear that you possibly have the problem solved, but don't just presume it was the battery. In case there is a charging problem that caused the battery to die, get the charging rate of the alternator checked with the new battery.

 

Any quick and easy way to figure that out? With the truck running and the volt meter connected to the battery, I'm showing about 13.98 volts.

 

That sounds about right but don't trust the in cab volt meter. It is just a guide. You could place your DC voltmeter on the battery and rev up the engine to about 1500 rpm and check the voltage. Do the voltage check with no electrical load and then another one with everything switched on. As long as it is between about 13-14 volts you should be good to go.
Maybe someone else has a comment on this?

 

The reading I listed was using the digital volt meter...factory gauges are about worthless. The reading was pretty consistent at idle and higher RPM, headlights on, etc.

Thanks again!