2003 Chevy Suburban Blower is draining battery

Check your blower control module located under the dash on the passenger side. It will be a circut board. I had the same problem. Note to consider GMC will not be the same and Chevrolet.

On my 2003 Suburban w/ Automatic Temperature Control, I experienced issues w/ fan/blower that manifested itself in this manner. In AUTO MODE, Upon starting engine, fan/blower would not immediately come on in the front, but the rear air would blow good and was cold. The front fan seemed delayed and sometimes took 5 mins or so, then would eventually start to blow, but seemed weak. When attempting to adjust blower/fan speed manually, it didn't seem to work well, sometimes intermittent, and didn't have as much flow as it originally did. After two days, I finally had an instance in which the fan stayed on after shut down and key was removed from ignition, but it did spool down and stop. R&R'd blower control module in about 40 minutes and worked like new.