TM 9-2320-209-34-2-3 (5) Overheat switch. FRAME 1 1. 2. 3. 4. 5. 6. Connect jumper wire (1) by terminal screws (2 and 3). Start heater (4) and let it run until pilot light (5) glows. WARNING Coolant will be hot. Use caution when working near hot coolant. Severe burns could result. NOTE The jumper wire (1) bypasses the restriction thermostat and keeps the heater on HI heat. Measure temperature of coolant at outlet hose (6) by letting coolant run on thermometer. Heater (4) will overheat and burning will stop. Make note of the coolant temperature when burning stops. Temperature should be between 220°F and 250°F. Flip control switch (7) to OFF position. Let the blower motor stop. Take out jumper wire (1). If temperature is not as specified, get new overheat thermostat. Refer to para 21-6c and para 21-6e. END OF TASK 21-13