
TROUBLESHOOTING AND ELECTRICAL SYSTEM
Test Procedures
Page 11-46
2005 FE350 Gasoline Vehicle Maintenance and Service Supplement
11
Test Procedure 33 – Brake Light Relay, Continued:
10. If the brake lights do not operate with the relay bypassed, there is most-likely a problem in the brake light
circuit other than the brake light relay. Restore the wiring to the original configuration (not bypassed), and
proceed to step 13 for additional test procedures.
11. Test the voltage suppressor wire assembly.
11.1. Disconnect the voltage suppressor assembly (17) from the relay coil terminals
(Figure 11-47,
Page 11-44)
.
11.2. Using a multimeter set to the diode test function (
ç
), place the black (–) probe of the multimeter
on the voltage suppressor red wire (25)
(Figure 11-49, Page 11-46)
. Place the red (+) probe on the
blue wire (26). The multimeter should indicate an overlimit with no tone emitted.
11.3. Reverse the multimeter probes and observe the multimeter. The multimeter should continue to indi-
cate an overlimit with no tone emitted.
11.4. If a tone is emitted (indicating a closed circuit) then the voltage suppressor has failed closed and
should be replaced.
12. Test the brake light relay coil.
12.1. Remove the voltage suppressor wire assembly (17) from the relay (10) coil terminals
(Figure 11-48, Page 11-45)
.
12.2. Using a multimeter set to 200 ohms, place the black (–) probe of the multimeter on one of the relay
coil terminals
(Figure 11-50, Page 11-47)
. Place the red (+) probe on the other relay coil terminal.
The coil resistance should be between 139 and 171 ohms. If the reading is incorrect, replace the
relay.
See Brake Light Relay Removal, Section 12, Page 12-33.
12.3. Restore the wiring to the original configuration (not bypassed).
Figure 11-49 Voltage Suppressor Test
(DIODE) SETTING
(OVERLIMIT DISPLAY)
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
25
26