i have a 1990 dx honda civic 1.5 4 speed my alternator is charging. but i think there is an open

If you have aftermarket systems such as an anti-theft, alarm, remote starter, etc., I'd suggest checking those out first. A lot of times those are the components that drain the battery.

You need to do a parasitic draw test. To do this you're going to need an ammeter. From there you will unhook the negative battery cable and place the ammeter in series with the negative cable and the negative battery terminal. If the ammeter reads anything over 25-50 milliamps you have a problem. Start by pulling fuses one at a time and replacing them if the meter does not drop. If you do not do this you are going to have a mess of fuses all over the place. When you find the fuse that makes the meter drop that is the circuit that the problem is in, and it will give you a better idea of what you have to replace. As a side note verify that there is not a ton of corrosion on the battery terminals and that the battery cables are in good shape. Doing a voltage drop across the battery cables will verify if they are electrically sound. Also leave the volt meter hooked up to the battery and crank on it if the battery voltage drops below 9 volts while cranking the battery is the problem.