TM 9-4120-403-14
Inspection
(1) Loosen TEMPerature control thermostat knob setscrews and remove knob.
(2) Remove four screws and locknuts that secure rear panel.
CAUTION
Take care that sensing bulb capillary line is not kinked and that bulb and capillary are not cut or damaged
during removal
(3) Pull rear panel away from box as far as harness will allow.
(4) Check that leads are properly connected. (See wiring diagram, fig. 4-43.)
(5) Check that capillary line and sensing bulb are not damaged.
(6) Check TEMPerature control thermostat for signs of overheating or other obvious damage. Replace if damaged.
Test
(1) Using multimeter, place probes on the red and blue terminals.
(2) Turn TEMPerature control thermostat shaft fully counterclockwise.
(3) Check continuity. If temperature at sensing bulb is above 40 (50C), there should be no continuity.
F
(4) Slowly turn shaft clockwise until continuity is indicated. Turn shaft back and forth slightly to check that switch
contacts open and close on a very narrow band.
(5) Place multimeter probes on the red and yellow terminals.
(6) Turn TEMPerature control thermostat shaft fully clockwise.
(7) Check continuity. If temperature at sensing bulb is below 90 (320C) there should be no continuity.
F
(8) Slowly turn shaft counterclockwise until continuity is indicated. Turn shaft back and forth slightly to check that
switch contacts open and close on a very narrow band.
(9) Replace TEMPerature control thermostat if it fails any of the above tests.
4-62
