Having an issue with battery draining over night. I've traced it to main fuse box under hood. With every fuse and relay out of it it still pulls a load, only way no current is drawn is if fuse box is totally disconnected as in battery lead is disconnected from fuse box

 

I have heard the interior fuse box is prone to failure, but have not read about the main fuse box.

 

Hmm. I've never heard of that either but now you have me thinking about another of my vehicles that eats batteries. How do you test it?

 

Charlie, disconnect the negative battery cable, and use a multimeter set to millaamp to bridge between the negative battery terminal and now disconnected battery cable. Close all doors, tape down the hood ajar switch, and wait about 30 minutes for the ECU to go to sleep. If you have a serious drain, the meter will read several amps. Begin pulling fuses one at a time and find which fuse drops the readings on the meter. If you have to open the driver's door to pull fuses from the passenger compartment, note how many amps the meter raised when the dome light turned on, and keep that in mind.
A vehicle without any problems will have about a 0.1 amp drain from the clock, radio etc.

 

Neat! I'll try it! Thanks for the explanation.

 

Don't open the door. Leave it open and close the latch. Seen to many blown out meters because someone opened a door. Rest of the explanation, I will co-sign on.

OP, stranger things have happened....