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Trailer Light Taillight Converter Installation

The installation schematic instructions listed below are for a basic taillight converter for a car, truck, suv, van, etc. This installation is for a vehicle with a 3 wire system. (vehicle has amber turn signals or separate turn signal and stop bulbs). It then converts the taillight harness to a 4 way flat connector. Not recommended for BMW, Land Rover and Mercedes Benz vehicles, Ford Freestar or Mercury Monterey vehicles, 99 to 03 Ford Windstar, 99 to 06 Lincoln LS and ALL vehicles with tail lamp outage modules. Consult your owners manual before splicing into your taillight harness.

Taillight Converter Schematic


1.) Determine a suitable location for mounting the taillight converter in an out of the way spot near the left tail lights in the trunk or on the frame rail, if mounted under the towing vehicle.

2.) Ground the white ground wire by placing the ring terminal under an existing screw attached to a clean metal surface or by drilling a hole and use a self tapping screw.

3.) Disconnect the tow vehicle's negative (-) battery cable.

4.) Using a circuit tester or volt ohm meter (VOM), determine which wire attached to the left taillight assembly is the left turn wire. Attach the units yellow left turn wire to this wire using a blue wire tap or Scotchlok. Determine which wire is the taillight circuit and attach the module's brown taillight wire to it with a wire tap. Determine which wire is the stop circuit and attach the module red stop wire to it with a wire tap or Scotchlok. (for 3 wire systems only).

5.) Route the units green right turn wire to the right side of the vehicle. Determine which wire is the right turn circuit and attach the green wire to it with a blue wire tap or Scotchlok.

6.) Secure all loose wiring with cable ties.

Testing Procedure

With the ground wire connected and all of the other circuits attached, attach the ground lead of a circuit tester to the exposed ground terminal of the 4-flat end. Activate the tow vehicle left turn, right turn, tail and stop lights one at a time. Probe the three receptacles of the 4-flat end to confirm proper functions. If testing with a trailer, make the proper connections and do the same test as the circuit tester using the trailer lights. If a function on the trailer lights does not work properly, disconnect the trailer lights, turn functions on vehicle off and recheck function with the unit with a circuit tester. Then check the trailer wiring for potential circuit problems.

Estimating Trailer Amperage Per Circuit

Stop-Turn Lights 2 Amps each
Taillights 1 Amp each
Clearance and Marker Lights 1/2 Amp each

NOTE: For estimating use only. Amperage is rounded to the nearest whole value. May not apply in all cases. Always check with your tow vehicles owners manual about adding additional loads to your electrical system. Some 12 volt batteries produce up to 14.5 volts. Use a VOM (volt ohm meter) to test.

If you know the wattage of the bulbs on your trailer you can use the formula P = I X E

P = watts
I = amps
E = 12 (volts)

Vehicle Specific Trailer Harness

Simple plug in Vehicle Specific Trailer Wiring Harness by make, model and year.

More Taillight Converters

Trailer Wiring Diagram

Trailer Wiring Diagrams

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