Table 4-2. Unit Troubleshooting.
TEST OR INSPECTION
ALL LAMPS DO NOT LIGHT.
Check for open circuit in wiring.
With tractor lights turned on, check tractor-to-semitrailer connector (1) by measuring voltage
between ground contact (D) and other contacts.
If measurement is not approximately 24 volts, refer to tractor operator's manual to perform
A. LEFT B.O. TAIL
B. LEFT SERVICE STOP
C. RIGHT B.O. TAIL
E. SERVICE TAIL AND CLEARANCE
F. B.O. STOP
H. B.O. CLEARANCE
J. RIGHT SERVICE STOP
Check receptacle (2) by measuring continuity between ground contact (D) and other bare metal on
If measurement is not zero, remove, clean, and install ground wire (3).
If measurement is still not zero, replace receptacle (2) (para 4-18).