Table 4-2. Unit Troubleshooting
TEST OR INSPECTION
Make sure all electrical power is disconnected before performing any maintenance on the electrical
system. Serious injury or death may occur if safety precautions are not observed.
The following procedures are applicable to the 12-volt and 24-volt electrical system.
1. ALL LIGHTS FAIL TO LIGHT
Step 1. Checklightswitchontowingvehicle.
Place light switch on towing vehicle in proper mode of operation. If towing vehicle lamps
light but semitrailer lights do not, proceed to step 2.
Step 2. Inspect for dirty or corroded terminals (1) in intervehicular cable receptacle (2) and
sockets (3) in plug (4).
If terminals or sockets are dirty or corroded, clean them.
If terminals or sockets are clean, proceed to step 3.
Step 3. Check to see that intervehicular cable is properly plugged
into 12-volt (1) or 24-volt (2) receptacle. In all steps, check
for good ground connection.
If cable is not properly connected, reconnect cable.
If cable is properly connected and ground connection is
tight, proceed to step 4.