TM9-2320 -363-20-1 Table    3-1. Troubleshooting (Cont) Malfunction Test   or   Inspection Corrective    Action ELECTRICAL SYSTEM    (CONT) Headlight Circuits    (Cont) Step   2. Disconnect  connector  from   right  headlight.  Check for   continuity    between ground    and   connector on    right   headlight at   lead    22D. . if   continuity is   present, go   to   step    3.    if   no   continuity    is indicated, replace right   headlight (page 4-206). Step    3. Disconnect right   low/high beam relay    from   connector. Check    for   continuity between lead    22D and    connector 87A. . if   continuity is   present, replace right   low/high    beam    relay. if   no continuity is   indicated, repair    lead    22D (page    3-2). Marker   and    Taillight Circuits 1.   NONE OF    THE MARKER LIGHTS AND TAILLIGHTS OPERATE. Step 1. Check    tractor    tail    marker 15A    fuse. l if   defective, replace 15A   fuse    (page 4-204). Step 2. Disconnect connector on   vehicular light   switch. . install    jumper wire    between connector 420F and   pin   F   on switch. Check for   +12    VDC at   pin   H. . if   +12 VDC is   present, repair lead    420H (page    3-2). if   no voltage is   present at   vehicular light   switch,    replace    vehicular light   switch (page 4-170). 2. LEFT FRONT MARKER LIGHT NOT OPERATING. Step 1. Step 2. Step    3. inspect    light   bulb. . Repliace    if   broken    or   defective (page 4-218). Remove lamp   from   socket (page 4-218). Check for   continuity    between contacts    of   lamp. . if   continuity is   indicated, go   to   step    3.    if   no   continuity   is indicated, replace lamp    (page    4-218). Check    for   continuity between socket    and   ground. . if   continuity is   indicated, go   to   step    4.    if   no   continuity   is indicated, repair    ground    lead    (page 3-2). 3-34