battery draining

i have a 92 mustang 2.3, have to jump start it every now and again, sometimes it shows alt not charging other times its up to where it should be. wheni have to jump it the battery is dead new battery, had alt tested and shows it is charging fine. took it off and took it to advance auto to have it tested. my tester doesnt show the alt working until i rev it up would it be the alt needs replacing cuz its not charging at low rpms? or is there something else like a bad switch that is draining the battery.
with lights on gauge goes low for nite driving.

any help appreciated thanks

First clean and tighten all the battery cables and wires to the alternator. If you have a slow drain it can be found by connecting a 12v test light between the positive cable of the battery and the positve post. If the light comes on with everything supposedly shut down, you have a drain. To find it leave the light connected and start pulling fuses. When the light goes out after you've pulled a fuse, that's the circuit that's draining the bat. Make sure before the test there's not a door, trunk, or hood open that uses a light.

The charging not being sensed by your VOM is probably due to a low set idle. It wouldn't cause the battery to go dead.

ok i tried that. did one fuse at a time. and there is still a draw on the system is there possibly something in between the fuse box and battery? i disconnected the wires off the starter relay and then connected to the one wire that gives me a reading and still a slow draw on the system. battery goes down so it wont start within hours
or am i possibly doing something wrong? here
thanks again?

pulled every fuse out of the fuse box and still a draw on the system? now where do i look unhook wire to the a/c? alternator? still a slow draw im goin to unhook about every connecto i can find 1 at a time

Try unhooking the alt. The diode could be draining amperage from the battery.

thanks for the reply i already found it before you posted and thats it. diodes draining battery. replaced alternator and its fine now. didnt wanna take a chance on just replacing the diodes and not rebuilding the whole thing as its been in quite a while. i had unhooked the alt but at that time it wasnt draining so its hard to find when there is no draw on the system.