Slow Battery Drain

You can disconnect the positive cable and check for draw between the post and clamp. A voltmeter will give you a reading that doesn't necessarily mean much. Same with a test light. 12-14volts will light a small bulb but it's the amps that tell you how bad the draw is. Most DVOM's (digital volt/ohm meter) will measure amps but are usually fused for 10 amps. If you tie into a unknown draw you may blow the internal fuse in the meter. Some of the old time mechanics use a headlight as a draw tester. If it's bright it is a pretty serious draw. If it just glows not a big draw. You can remove one fuse at a time to see which circuit is causing the issue.