TM 9-2320-361-34 17-19. ENGINE COOLANT HEATER TESTING (Contd) f. Restriction Thermostat Test 1. Place switch (4) in START position. 2. When indicator lamp (5) illuminates, place switch (4) in RUN position. Allow heater to run. 3. Check temperature of coolant at thermometer (1). Temperature should be 140-170° F (60.0-76.7° C). Replace restriction thermostat if coolant temperature is not within limits (para. 17-4). 4. Place switch (4) in OFF position. g. Overheat Switch Test 1. Place switch (4) in START position. 2. When indicator lamp (5) illuminates, place switch (4) in RUN position. Allow heater (8) to run. 3. Partially restrict air inlet with a sheet of cardboard or sheet metal. Overheat switch (9) should activate and shut down heater (8) within five minutes. Replace overheat switch (9) if heater (8) does not shut down after five minutes (para. 17-7). 4. Check temperature of coolant at thermometer (1). Temperature should be 220-250° F (104.4-121.1° C). 5. Replace overheat switch (9) if coolant temperature is not within limits (para. 17-7). 6. Place switch (4) in OFF position. I h. Test Equipment Removal WARNING Allow time for heater to cool before removing from test equipment. Failure to do so may result in injury to personnel or damage to equipment. 17-54 1. Disconnect lead (2) from 24-volt power source (3). 2. Install guard (6) on heater (8) with four screws (7). 3. Remove heater (8) from test equipment.