Blower motor continues to run when vehicle is off

It is located on the outside of the air ducting just off from the blower motor. Hope that helps.

Your problem is the Relay which is encased inside the Heater/AC Resistor Module. This is a very common problem with GMC and Chevy Trucks. The Relay's return spring fails and the relay is held closed by gravity. The only fix is to replace the Resistor Module. I have a 2004 Silverado and have replaced the Module 3 times and the Blower Motor twice. The Orange wire feeding the Module is always Hot (12V) and feeds the Relay Contact for Highest Blower Speed. Hence the Blower runs all the time even with the Key off and removed.