When you turn your blower on AC or just vent it drains your battery with in 30 second what would cause this in a 99 ford explorer?

I assume you have the engine running - Your alternator is not charging for some reason. The alternator runs all the auto electricals and keeps the battery charged to restart the next time. check your charging system, and battery... Everyone should have a manual for their vehicle, and a professional shop manual should be available at your local library for diagnostic procedures etc, just make copies of the right pages, as they are usually REFERENCE only...read up and good luck :)