TM 9-2320-209-34-2-3 f. Functional Test. FRAME 1 1. Make sure emergency switch (1) is in ON position. 2. Pull AIR control knob (2) all the way out. 3. Set heater motor switch (3) to START position,. Hold switch in this position for at least 10 seconds or until indicator lamp (4) lights. 4. Set heater motor switch (3) to RUN position. NOTE If heater motor switch (3) is moved to RUN position before indicator lamp (4) lights, heater will not work. 5. Set blower switch (5) to LO position, then set switch to HI position. 6. A change in blower speed should be noted. Air coming from heater should be very warm. 7. Set heater motor switch (3) to OFF position. 8. Push in AIR control knob (2). END OF TASK 21-139