
TROUBLESHOOTING AND ELECTRICAL SYSTEM
Test Procedures
2005 FE350 Gasoline Vehicle Maintenance and Service Supplement
Page 11-49
11
TEST PROCEDURE 35 – VOLTAGE AT TAILLIGHT SOCKET
See General Warning, Section 10, Page 10-1.
1. Disconnect the battery cables as instructed.
See WARNING “To avoid unintentionally starting...” in
General Warning, Section 10, Page 10-1.
2. Remove the taillight lens and remove the light bulb from the socket
(Figure 11-52, Page 11-49)
.
3. Using a multimeter set to 20 volts DC, place an alligator clip on the multimeter black probe. Connect the
black (–) probe to the ground terminal (where the black wire is attached) on the back of the taillight
assembly.
See following CAUTION.
ý
CAUTION
• Do not allow the multimeter probe to touch the wire contact (+) and the metal housing (–) of
the light bulb socket assembly at the same time. An electrical short could occur which could
blow the fuse or cause wire damage.
4. To test brake light circuit, place the red probe on wire contact connected to the 18-gauge red wire.
5. To test taillight circuit, place the red probe on wire contact connected to the 18-gauge brown wire.
6. Connect battery cables, positive (+) cable first, and tighten hardware to 12 ft-lb (16 N·m).
7. To test taillights, place light switch in the ON position. The reading should be approximately 12 volts.
8. To test brake lights, place the light switch in the OFF position and press the brake pedal, making sure the
park brake is not pressed. The reading should be approximately 12 volts.
9. If the reading is incorrect, check bulb socket and wire continuity.
TEST PROCEDURE 36 – TAILLIGHT BULB SOCKET
See General Warning, Section 10, Page 10-1.
1. Disconnect the battery cables as instructed.
See WARNING “To avoid unintentionally starting...” in
General Warning, Section 10, Page 10-1.
2. Inspect wires at the light bulb socket. Make sure wires are securely fastened to the contacts inside the
socket
(Figure 11-52, Page 11-49)
.
3. Inspect the socket housing to make sure there is no corrosion on the contacts or inside the housing.
4. Inspect the light bulb and make sure there is no corrosion on the bulb contacts.
Figure 11-52 Taillight Socket Voltage Test
LEFT
TAILLIGHT
BLACK
WIRE
2m
20
m
200
m
2k
200
200
200
200
20
2
200
m
500
20k
200k
2000
k
1000
OFF
WAVETEK
5XL
V
V
V
A
!
!
COM
200nA
MAX
1000 ---
750V
FUSED
20 VDC SETTING