Troubleshooting Hints - Exterior Lights
Perform before beginning System Diagnosis^ Check for a broken (or partially broken) wire inside of the insulation which could cause system malfunction but prove "GOOD" in a continuity voltage check with a system disconnected. These circuits may be intermittent or resistive when loaded, and if possible, should be checked by monitoring for a voltage drop with the system operational (under load)
^ Check for proper installation of aftermarket electronic equipment which may affect the integrity of other systems (Refer to "Diagnostic Aids/General Troubleshooting Procedures,"). Diagnostic Aids
^ Make sure all lamps are operational before replacing flashers.
^ Refer to System Diagnosis. System Diagnosis - Exterior Lights