TM 9-4120-403-14
Inspection
(1) Loosen setscrews and remove thermostat knob.
(2) Remove four screws and locknuts that secure panel.
(3) Pull rear panel away from box as far as harness will allow.
(4) While holding rear of switch, remove nut, lockwasher and keyed washer from threaded shaft.
(5) Check switch to see that the leads are properly connected (see wiring diagram fig. 4-43).
(6) Tag and disconnect wire leads.
(7) Repair or replace loose or broken leads.
(8) Check that switch terminals are not loose, broken, or corroded.
(9) Check switch for evidence of overheating or other visible damage.
(10) Replace switch if damaged.
Test
(1) Using multimeter, place probes on terminals 1 (center) and 3 (bottom).
(2) Place switch in up position (HI SPEED). Continuity should be indicated.
(3) Place switch in down position (LO SPEED). No continuity should be indicated.
(4) If the switch fails any of the above tests, replace switch.
Replacement
NOTE
Fan speed switch provided as original equipment has center terminal marked "1" and bottom marked "3".
Replacement switch may have numbers cast in body different than original. Be sure to wire between
center and bottom terminals.
(1) Install nut and lockwasher onto switch shaft.
(2) Install switch in control panel.
(3) Slip keyed locking ring on threaded shaft and align with hole in control panel.
4-65