TM 10-3930-669-20 VISUAL INSPECTION (1)  Set  MAIN  POWER  switch  to  ON position (TM 10-3930-669-10). (2)    Set    engine    switch    to    ignition position (TM 10-3930-669-10). (3)  Turn  on  both  cab  lights  (TM  10- 3930-669-10). (a)   If   one   cab   light   operates, fault   is   between   lamp   and lead wire.  Perform Steps (4) through  (6)  below  and  go  to Step 2 of this Fault. (b)    If    no    cab    lights    operate, perform   Steps   (4)   through (6) below and go to Step 4 of this Fault. (4) Turn off both cab lights. (5) Set engine switch to off position. (6) Set MAIN POWER switch to OFF position. 2-189