Battery Drain??

[Moab4x4]

I have been having a problem with a dead battery if I leave the truck sitting for more than a week or two. This time of year, I don't drive much. I have been charging the battery but I think I killed the battery by letting it get too dead a couple of times too many.

I decided to go to a dual battery setup (thanks DValentine for your pics) and it sure spins faster in the morning now. But I noticed as I hooked things up last night in the dark that I got a small spark as I hooked up my ground. Cab doors closed, no lights on, key out of ignition. No visible load. When I disconnect the wire from the alternator, I don't get the spark when I hook up the ground to the battery.

I see three possibilies, 1. I have a blown diode in the alternator or something that draws current when it is off.

2. There is always a draw, but with good batteries we just don't notice it.

3. There is some capacitance in the wiring harness that caused the first spark, but it was charged up the second time and unhooking the alternator was a fluke and really didn't mean anything.



Does anyone have a clue what the "off" leakage current should be on our trucks? I haven't hooked up a meter for lack of time, but was wondering if anyone else has or if anyone else has any ideas.



Thanks,

Ken

 

[TJJEEPER]

Ken, Your radio will draw a tiny amount. It uses 12V to keep the station presets and clock set. Not enough to drain the batteries in a couple weeks though. I don't know enough about the 1st gens to know if there is any type of computer on board or not. If there is then they will draw a bit too. Again, not enough to drain the juice in a couple of weeks.

 

[KOG]

You've already diagnosed the problem. Spark with alternator connected, none when disconnected. It's a bad positive diode. Radio and computer will drain a car battery in a month or so, will take 2-3 months to drain the battery on a CTD.

 

[Moab4x4]

I suspected the diode, but alternators are not my specialty.

Thanks for the input.

Ken