i have a 98 blazer that if i leave it sitting overnight without disconnecting the neg battery cable the battery is dead as hell when i wake the next morning. i guess what i'm asking is, is this an issue with many blazers or not so i might have an ideal where to look first. i'm thinking that it has something to do with the heater vents cause it makes odd sounds behind the dash. anyways thanks for the help. It is a LT model if that helps any.

 

You have to isolate the circuit that is causing the draw. Start by disconnecting the negative battery cable and install a multimeter inline with the cable & battery. Then remove all of the fuses and reinstall them one at a time, recording the amperage draw when each fuse is inserted. You will have to wait up to 5 minutes or so for a particular component to reach its lowest power state (sleep mode).

You could look try just pulling fuses individually and recording the impact on the amperage draw much the same way. Your truck should not draw over 35mA (0.035A) after everything has gone to sleep.

It will be tedious.

 

Could be that your battery is going bad. You say that there is something "running" in the back of the dash?

 

i hear noises behind the dash only when its running. I also know its not the battery it started with the old battery then i put a new one in not long ago after it killed that battery i took it back to the store and had em test it 2 times it tested good both times.

 

What kind of noises behind the dash? The fan door inside my '94 went bad and it would sound like it was trying to open and close and I would hear what sounded like gears grinding.