howdy - I have a quirky 1990 F-250.

Bought it back in 2005.  Had few if any problems with it - it always
started up and ran fine. Just didn't drive it much.

After 6 months, I forgot to turn off the dome light, and the battery
went dead.  Replaced the battery in late 2005, and started it up and ran
it around every couple of weeks.

Started to use the cab for some tool strorage and I guess a box or
something eventually fell off a pile of other boxes, and bumped up
against the power lock switch, and I guess that constantt operating of
the pwoer door lock switch killed the second battery.  So I clearned out
the cab, got a new battery, and thought my problems were solved.  Went
back two weeks later, and the battery is dead again.

Any ideas what I should do?  Get a new battery and do a starting system
check?  Could something in the alternator kill the battery while the
truck isnt' even turned on and running?  Could there be a short in the
power door lock switch?  Or a short anywhere else?