Table 4-2. Unit Troubleshooting Procedures (Con't).
TEST OR INSPECTION
At each affected light, check continuity between ground side of light socket and
frame. DO NOT remove light housing while making this check (see paragraphs 4-20,
4-21, 4-24 through 4-26, or 4-28).
If there is continuity, proceed to step 9.
If there is no continuity, check light for damaged or corroded housing. Check
for loose or corroded screws mounting light to semitrailer. If screws are loose,
tighten. If any component is damaged or corroded, replace (see paragraphs
4-20, 4-21, 4-24 through 4-26,
At each affected light, visually check button contacts inside light socket for
looseness, corrosion, or other damage.
If button contacts are loose, corroded, or otherwise damaged, replace (see
Use an extension wire, as required, long enough to reach between
Location of connectors will vary with light being checked. If connector is
inside light box at rear of semitrailer, stop/taillight must be removed (see
Step 10. At each affected light, trace circuit between button contact at light socket and first
connector. Check continuity in wire between button contact and first connector.
Check for a short in same length of wire. Check for loose, disconnected, or
damaged connectors and wires.
If there is continuity, that length of wire is O.K.
If there is no continuity or if wire is shorted,
Step 11. Check for continuity and a short in wire between first connector and next connector.
Repeat wire checks until circuit breaker in voltage control unit at front of semitrailer is
reached. Check for loose, disconnected, or damaged connectors and wires.
If there is no continuity, or if wire is shorted, replace wire (see
Step 12. If malfunction still exists, replace voltage control unit (see paragraph 4-14).