RAM 2500 diesel battery dies
 

My 1992 Dodge diesel pickup's battery dies if I don't run it every few days. After jump starting it for several weeks, I put a new 1080 amp battery in it and drove it to the service garage. They checked the electrical system and it was working right. I drove it home [24 miles] and it started fine for the next week. Then I was gone for two weeks and now it won't start again. The battery is dead. I assume there is a short in the system somewhere. What is the next step? I have the battery charging now, but I don't want to have to keep repeating this process.

once charged start the truck and put a voltmeter across your battery, it should read anywhere from 13.5 to 16 volts, showing that your alternator is charging your battery if it shows less than 12.5 Volts then there's a problem in your charging system, check belt on alternator is tight , all fuses for charging are OK ( if equipped with a fuse for charging system) if those are OK and it reads less than 12.5 volts, change your alternator.

If the alternator is charging your battery when running then you do indeed have a short somewhere.

first question to ask is :
Is there a system on the car that isn't working correctly ?... and... is there any wiring that has been worked on or disturbed recently ?... if yes, check those systems first for your short.

If not then you want to ... :
with the ignition off....
connect voltmeter across battery
disconnect one fuse at a time looking for your voltage to go up, when you see it rise on the voltmeter, you've got the system where the short is and need to check its wiring.

If that doesnt work then you have to go the long route and yank one fuse and leave it for a few days and see if it dies...repeat until done with all fuses...when you yank and it doesn't die, you've found the system with the short.

Logically, you can try to narrow it down a little by saying... what systems have electricity at all times and check those first, this is a rational guess based upon statistics... since the day the truck was built your radio, ecm, alarm, alternator and starter all have electricity running to them 24/7 so if something were to wear out its most probably in one of those systems... my experience has shown if its not the alternator or starter ( which I doubt in your case because the battery lasts a week and those components would run it down in a day if shorted )... then its usually the radio itself, the alarm system or the ECM... because your battery lasts a week before dying, its a slow drain which to me indicates a non primary system such as radio alarm or ECM... but you need to test it all to be sure until you find it and there really is no easy way...

Thanks so much. Great instructions. I'll try them tomorrow.

RAM diesel
 

Apparently the short is in the electric door locks. When I reinstalled the battery, the door locks started cycling as soon as the second [+] cable touched the terminal. The owners manual shows door locks on #6 fuse, but it is supposed to be a 20 amp fuse. However, it is a covered [aluminum case] fuse, not a standard fuse. I pulled it and the door locks no longer operate. But neither does the radio, which should be on #8, a 10 amp fuse. I installed a new 10 amp fuse, but still no radio. I'll see if there is still a drain on the battery or if I have to pull the radio fuse, too.

Electric door locks and the radio (clock) are on the IOD fuse. Power seat is on that too. IOD is for Ignition Off Draw. Stuff that would run down the battery while parked.