Intermittent Battery Drain -- 88 5KQ

[b1biker at aol.com]

Fellow listers -- 
I've been chasing an intermittent battery drain on this vehicle for more than a year. I've had it in the shop wtwice and still can't find the problem. There does not appear to be any rhyme or reason to this problem; the car may set for a wek and be fine, or as the current situation, it was driven on Tuesday and this afternoon the battery was so low that with the battery hooked up my 12A charger could not generate enough current to actuate the door locks or the dome light. I'm at a loss for how to find the source of this problem but until I do I have a hard time counting on this for my primary transportation and that's what it's soon to be. Any help will be greatly appreciated.
Gary Meier