TM 10-3930-664-10 KEY OR CONTROL FUNCTION NOTE 4 Heater Blower Switch A three position push-pull switch controls the airflow of the heater.  Blower is OFF in the fully depressed position. 5 Defroster Fans Removes moisture or frost from front and rear windows.  Turn switch to "ON" position on front and rear fans to operate fans. 6 Door Release Lever Opens the cab door.  Lift the lever to open the door.  A catch on the outside will hold the door in a full open position. The following controls are installed only in Model MHE-271. 2-11