Something is draining the battery on my 1985 Ford Ranger 2.3 and alternator, starter and voltage regular tested as good. What else could be draining the battery?

The best way to find this problem is by disconnecting the negative terminal and connect a test light in between them. then see if the light lights up if so that is your drain,now start disconnecting fuses one by one until you find the one that turns off the light, what that fuse powers will be the cause of your problem. test light should not light if there is no drain.

Best thing to do is disconnect the neg battery terminal put your volt meter on amps and hook it up in series from the neg cable head to the battery neg and disconnect fuses one at a time until the draw goes away,then narrow it down from there