TM 9-2320-302-20
0010 00-7
Table 1. Electrical System Troubleshooting Procedures - Continued.
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
Blackout Light Circuits - Continued
4. One or None of Blackout (B/O) Drive Lights
Operate - Continued.
6. Check
for
+24
VDC
at
connector
421K
at
trailer
receptacle(s).
If
+24
VDC
is
present,
troubleshoot trailer circuit(s). If
voltage is not present, repair
lead(s) 421K (WP 0119 00).
Turn Signal and Stoplight Circuits
1. Stoplights Do Not Operate.
1. Check stoplight 20A fuse.
Replace 20A fuse if defective (WP
0071 00).
2. Inspect light bulbs.
Replace
bulbs
if
broken
or
defective (WP 0087 00).
3. 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
continuity
is
not
indicated, replace stoplight switch
(WP 0109 00).
4. 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
continuity
is
not
indicated, repair lead 420A or
420K (WP 0119 00).
5. 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
continuity
is
not
indicated, repair lead 420C or lead
36C (WP 0119 00).
6. Disconnect lead 36C from
vehicular light switch. Check
for +12 VDC in lead 36C with
stoplight switch closed.
If +12 VDC is present, replace turn
signal switch (WP 0073 00). If
voltage is not present, replace
vehicular light switch (WP 0063
00).
2. Left/Right Stoplight Does Not Operate.
1. Inspect light bulb.
Replace
bulb
if
broken
or
defective (WP 0087 00).
2. Remove
lamp
from
left
stoplight. Check for continuity
between contact points.
If continuity is indicated, go to
step
3.
If
continuity
is
not
indicated, replace lamp (WP
0087 00).
3. Remove
left/right
stoplight
lamp. Check for continuity
between socket and ground.
If continuity is indicated, go to
step
4.
If
continuity
is
not
indicated, repair ground lead (WP
0119 00).
4. Check for +24 VDC at turn
signal switch at lead 38B/39B
contact point.
If +24 VDC is present, replace turn
signal switch (WP 0073 00). If
voltage is not present, repair lead
38B/39B (WP 0119 00).
