Brake lights but no tail lights?

USING A VOLTMETER

THE TRUCK END HAS 3 FEMALES AND ONE MALE CONNECTORS

SET V-METER TO OHMS

THE MALE CONNECTOR (WHITE) SHOULD HAVE "CONTINUITY" TO "GROUND" ON THE TRUCK

NOW SET VOLTMETER TO "20 VOLTS DC OR SIMILAR"

THE FEMALE (BROWN) CLOSEST TO THE MALE SHOULD HAVE 12 V WHEN THE RUNNING LIGHTS ARE ON

THE MIDDLE FEMALE (YELLOW) SHOULD PULSATE THE METER WHEN LEFT TURN SIGNAL BLINKS

THE FURTHEST FEMALE (GREEN) FROM THE MALE SHOULD PULSATE THE METER WHEN THE RIGHT TURN SIGNAL IS ON

YELLOW AND GREEN SHOULD BOTH GET A STEADY 12 V WHEN THE BRAKE IS DEPRESSED----AND THE TURN SIGNALS ARE OFF

MOST PROBLEMS I HAVE SEEN WITH THE TRUCK PIG TAIL IS WIRED INCORRECTLY. CHOPPED INTO THE WRONG WIRES (FUEL SENDER, ETC)

ON THE TRAILER END.

RELYING ON THE BALL TO BE A GOOD GROUND--HAVING NOT CONNECTED THE WHITE ON THE VEHICLE END

THE GROUNDS TO THE LIGHT FIXTURE HOUSING ARE BAD--THE RUNNING LIGHTS AND TURN SIGNALS SEEK GROUND THRU EACH OTHER AND USUALLY BOTH BLINK "DIMLY" WHEN SIGNALS ARE ON

THE TRAILER LIGHTS ARE WIRED INCORRECTLY--- SUCH AS: THE RUNNING LIGHTS ARE HOOKED TO THE BRIGHTER BULB'S FILAMENT. AND THE TURN SIGNALS TO THE DIMMER BULB'S FILAMENT (MANY DO NOT KNOW THERE "IS" A BRIGHTER FILAMENT, AND JUST HOOK TO WHATEVER WITHOUT "TEST", PRIOR TO HARD-WIRING THE SYSTEM)

BOAT TRAILERS ARE THE WORST FOR CORROSION IN THE LIGHT SOCKETS AND CONNECTIONS.'SPECIALLY SALT WATER

LET ME KNOW IF THIS IS THE INFO YOU WANTED

THE MEDIC