Many circuits are hot all the time, headlights, brake lights,hazard lights, radio amp, key fob, door switches, interior lights, under hood switch light, accessory sockets, etc... None cause a draw unless activated. Aftermarket accessories are the most common cause.

 

UPDATE:

Had my mechanic diagnose it after I gave up, the blower motor was the cause of the battery drain. They confirmed it today leaving the blower motor unplugged with the battery connected, and the battery is not drained. I have ordered a new blower motor and blower motor resistor that I plan to install this weekend.
So if you're having a random battery drain issue, and you've checked all aftermarket stuff, check your blower motor and resistor. Judging by how many of these resistors have been sold on eBay this looks to be a common issue (I bought a rebuilt one from Module Repair Pros).

 

Final update on this thread: I replaced the blower motor and resistor, battery has not drained at all since. They're both located on the passenger side under the glove box. Case cracked.

 

2003 H2 chasing the exact same issue:

I unplugged that resistor and Stil had a phantom / parasitic drain overnight two days ago.. it was starting well for 4 days, then back to the dead battery.

Are there two connections?

thanks !

 

yes try unplugging the blower motor itself not just the resistor, or pull the fuse
you can verify if its your blower motor by connecting a multimeter the way they show in that youtube video above to your battery, you should see a constant drain, pull the fuse to the blower motor and see if the drain goes away

 

Seat control circuit is another known cause of draining with key off/out.

 

Thanks - found it.

 

what was the drain?

 

Drain I was referring to is related to the Sunroof - one is still clogged and we have had that issue off and on for years.. The channel in the sunroof collects water and when drains are clogged, it overflows to the headliner..flows and dumps in your lap or down a pillar behind dash.. not good at all for elec..

 

Apologies,, I am chasing two issues.. A DRAIN hose, and a Parasitic Drain on the Battery.
I have not identified (though testing) the actual drain on the battery. We are chasing that and unplugging systems..
I tried using a meter to detect the drain and had no success as it is random.