intermittent battery drain??

[npauli]

When the truck has been sitting, at the next start it either
1) cranks strong and fires right up, or
2) cranks really slow, and sometimes needs a jump.

I've had 2 weak starts and 1 jump start in the last few days. No problems when warm.

No, I didn't leave the lights on. Don't have anything plugged into the lighter either.

My best guess is some relay is sticking from time to time. Does that sound plausible? Anything else it could be?

What's the slickest way to track down a battery drain? All I can think of involves pulling fuses one by one and looking for current either across where the fuse goes or between the battery and cables.

[npauli]

Just finished looking through old posts on the subject. Sounds like:
1) I wasn't far off with pulling fuses
2) Replacing batteries might help (I'm about due anyway), but might just cover up the underlying problem
3) I might want to unplug that brake controller that I never use.
4) Starters, alternators, and funky grounds or battery balance issues are common causes.

I'll try pulling fuses tomorrow and see what I can find....

[npauli]

I tried several times to find current with engine off - no luck. Eventually gave up and decided to try new batteries. Glad I did. When I went to pull the old ones, the driver side battery was hissing, spitting a little acid out the vent, and was ~ 150F on the sides. It was down to 10.X volts too. Maybe the good battery was wearing itself out trying to charge the bad one.

She cranks real nice now, and no voltage difference between batts, and no current when the engine's off. Crossing my fingers...

[JohnC]

Sounds like your left battery had an internal short. It may have been intermittent, but you're better off without it!

Yes, one bad battery pulls the good one down too.