TM 9-2320-363-20-1 Table    3-1. Troubleshooting (Cont) Malfunction Test   or   Inspection Corrective    Action ELECTRICAL SYSTEM   (CONT) Turn   Signal    and   Stoplight Circuits    (Cont) 1. NEITHER    STOPLIGHT    OPERATES. Step 1. Step    2. Step 3. Step    4. Step 5. Step 6. Check stoplight 20A fuse. . If   defective, replace 20A    fuse    (page    4-204). Inspect light   bulbs. . Replace if   broken    or   defective (page    4-284). Disconnect leads    420A and    420K from   stoplight    switch.    Check    for   continuity between switch    contacts while pressing switch. . If   continuity is   indicated, go   to   step    4.    If   no   continuity   is indicated, replace stoplight   switch    (page 4-228). Disconnect leads    420A and    420K from   vehicular light   switch.    Check    for continuity    between leads 420A and   420K with   stoplight   switch   closed. - If    continuity is indicated, go to step 5. If no continuity is indicated, repair lead 420A or lead 420K (page 3-2). Disconnect lead 420C from vehicular light switch. Disconnect lead 36C from turn    signal   switch. Check for continuity between lead   420C and   36C. . If   continuity is   indicated, go   to   step    6.    If   no   continuity   is indicated, repair lead    420C or   lead    36C (page    3-2). Disconnect lead    36C from    vehicular turn   signal    switch.    Check    for   +12    VDC in   lead    36C    with    stoplight    switch   closed. . If   +12    VDC is   present, replace turn signal switch (page 4-168). If no voltage is    present, replace vehicular light switch (page 4-170). 2. LEFT STOPLIGHT NOT OPERATING. Step 1. Inspect light bulb. . Replace if broken or defective (page 4-284). Step 2. Remove lamp from left stoplight (page 4-284). Check for   continuity   between contact    points. . If   continuity is   indicated, go   to   step    3.    If   no    continuity is indicated, replace lamp (page 4-284). Step 3. Remove left stoplight lamp. 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). 3-42