TM 5-5420-226-20-1 DETAILED TROUBLESHOOTING PROCEDURE SUPPORT SYSTEM -   VEHICLE LIGHTING Symptom-65 ONE HEADLIGHT BLACKOUT MARKER LAMP OR    ONE TAILLIGHT BLACKOUT MARKER LAMP WILL NOT LIGHT. ~ ~~T~ This   procedure is to  be  performed by two persons. The lead person is referred to  as  the  first   technician and shall  direct    the  activity of  the  second person    called    the   second technician. Check if  one   headlight blackout marker lamp   or   one taillight blackout marker lamp    is  not   working. Second Technician (Operator’s Station) l   Set   MASTER BATTERY switch ON. l   On   LIGHTING CONTROL switch, turn    LIGHTING CONTROL lever    to   B.O.    MARKER. First Technician (Front of   Vehicle) l   Visually   check    headlights to  see  if  one   blackout marker lamp is   not    lit. First Technician (Rear of   Vehicle) l   Visually    check   taillights to   see   if  one   blackout marker lamp is  not    lit. Is  one   headlight blackout marker    lamp   or  one   taillight blackout marker lamp    not   lit? I I&l I D ,e ‘.  K’ 0,.  <,0”1 WJl ~~d MASTER CONTROL PANEL FOR CLARITY QUADRANT ASSEMBLIES NOT SHOWN l   Check    headlight baae    harness connector (CKT    20),   at headlight assembly that    does B.O. not   work, for   electrical power. MARKER HEADLiGHTS o l   See   Step 6 . \ I TA107326 4-637