Battery Drain

[guruerror]

Here and there I've seen threads about dead batteries and parasitic drains but none mention what I've discovered and I thought I'd through this out here to get your thoughts.

I've notice that if I leave the rear hatch open for an extended period of time (4 or more hours) the battery will drain so low that I cannot start the truck. The first time this occurred I assumed that the interior lights must have been on the entire time and that they were the culprit, but the interior lights don't stay on for the whole time...they turn off after a few minutes to guard against a battery drain when a door is accidentally left ajar.

SO...if the lights turn off automatically WHAT would continue to drain the battery when the rear door is open.

This has happened to me at least three times...so now I'm overly conscious of leaving the door ajar, but thought I'd mention it in case someone had a thought on how to resolve...or where next to look.