GMC Repair: 2003 GMC Envoy Rear Blower, gmc envoy, hindsight

Question
Can not control the rear blower.  Runs @ high speed even when rear control is set to 0 (zero) and main dashboard control is off.  Hindsight, blower would cycle through speeds automatically, now it continues to run.  It does turn off with the ignition off, unlike some other postings I've read.  Any help would be appreciated.

Answer
sounds like the blower itself is bad or the blower control module, does it ever work correctly from the switch?  if you can, remove the blower control head from the center console and unplug it if it turns off, check the terminals in that connector if they appear to be clean then you may have a bad control head