Why did my battery drain on my GMC Jimmy 1999?

[kyle]

Okay, so I had a new alternator and battery put in 3 months ago. Well a few days ago I woke up and my inside lights were on. Not sure how long they were on. My voltage meter showed it was 11 when it should be 14.. that was with it running. When I did not turn it all the way it went to 8 or 9.. now its completely dead.. the battery. It wont start, but does try to click over. Also, we had to unplug the battery because the inside lights would not go off tonight. Is this a sensor problem? Could it have drained the battery, or possibly is it a bad alternator? If it is a bad sensor which drained the car, then how would that be fixed? Also, before it died.. I drove it just fine to work and back with the AC on, and the voltage level stayed around 11

 

[Alex]

12.4v is normal battery voltage with the car off. If your car is reading 11v while started then you either have a bad alternator or a short somewhere in the wire harness

 

[Joe E.]

god hates you

 

[Desert Dust]

Yes, domes lights have been known to drain more than a few batteries. I would try and get the truck jump started. Then read the voltage with a real voltmeter not that silly thing on your dash board. A a fast idle if it's not reading 13-14 volts across the battery, then I would take it back to the shop that replaced the alternator.