if you unplugged the blower motor, and it continued to run, then you sir or ma'am have just invented a new perpetual motion machine. But in all seriousness, a bad resistor pack will prevent the blower motor from operating at any speed except on high. The "high" setting bypasses the resistor pack and applies direct voltage to blower motor. If, however, your motor is stuck running all the time at high, then something has shorted, and it is receiving full 12V voltage, regardless of switch position. Try tracing harness from motor back, and look for any abrasions or cut wire insulator. You replaced switch module but check at that end too for problems with harness.