2001 Dodge B3500 van mystery battery drain. UPDATE

SUMMARY: Did parasitic drain test. Battery drain reads .13A. Did the remove-and-check each fuse and relay both under hood and inside.
When I removed under hood fuse "Battery Feed #2" (40 amp) drain drops to .04A. "Battery Feed #2" circuit causing battery drain. What is it ?
Did this test 3 times for same result.
Will van run with fuse pulled? Disconnected alternator...no difference, so it is good. Checked out van wiring diagram...unfortunately I cant read them. WHAT TO DO NEXT???? THANKS

 

The diagrams I have access to, show that fuse as "Van conversion provision".... So, apparently, it powers something the conversion company installed.....

 

Yep. I have a secondary fuse box in the back of the van that has circuits for the rear AC, the disco lights, the VCR and the TV.

Also I know I am late to this, but if you have a second battery that isnt the same electrical/charging shape as the primary one, the second battery can drain the primary and if the second battery is really crap, it can totally kill the primary. This happens in boats all the time.

 

Thanks for your ideas. I think the "van conversion" circuit is suspect. I'm pulling the fuse and see fig battery drains in a couple days. I don't care about the "van conversion" accessories anyway. No, don't have a secondary battery system.