No Light Signals at 4-Pole Connector After Installing Curt Harness C59496 in 2001 Lincoln LS  

Question:

Expert Reply:

If you have no light signals at all at your 4-pole connector (no turn, tail or brake lights) then either the powered converter in this harness may have been damaged in the first installation effort, there is a faulty 12V input power connection to the converter, a bad ground connection or there is a problem within the wiring in the vehicle or trailer.

The installation instructions are included in this email in case you no longer have the original printed copy. I have also linked an article on troubleshooting 4-pole trailer wiring. You will need a circuit tester like the # PTW2979.

First carefully review the installation steps in the instructions. It is important that the instructions be followed precisely or damage to the powered converter or a malfunction could occur.

Disconnect the battery negative terminal. Cut the wire on the (empty) fuse holder; connect one side to the battery positive terminal using the ring terminal and connect the other side to the black wire using the butt connector and route this wire to the blue wire on the harness (which is labelled battery). Connect the black and blue wires. Confirm that the T connectors are fully attached to the correct plugs on each of the Lincoln tail lights. (The wiring with the yellow wire is left-side and the wiring with the green wire is right-side). Firmly secure the white ground wire with eyelet to either an existing ground point behind the passenger side tail light assembly or select a suitable spot (a clean unpainted surface) and attach the white ground wire. Attach the converter box to the vehicle using the supplied double-sided tape. Reconnect the battery negative terminal and insert the fuse into the holder. (The red wire on the harness is not to be used.)

Now you can use the circuit tester on the pins at the 4-pole connector. Please refer to the attached photo. With the vehicle lights on, apply the grounded circuit tester to the pin for the brown tail light wire. You should detect a steady signal. Next one by one engage the vehicle turn signals and test the pin for the left turn (yellow wire) and right turn (green wire). These pins should carry an on-and-off blinking signal.

If your 4-pole carries all the correct signals then connect your trailer and test the brake, tail and turn lighting functions on the trailer. If you still have no lights on the trailer then there is a problem within the trailer wiring.

If you do not have the correct output on the 4-pole use the circuit tester on the wiring leading to the vehicle (input) side of the converter. Test each function one at a time. With the left turn signal engaged test the yellow wire for a blinking turn signal. Test the green wire from the passenger side harness with the right turn signal on. If signals are carried on the wires leading into the converter but there is no output, then the converter is bad.

If there is input to the converter and output from it, next you can move on to the trailer. Examine the 4-pole trailer connector for any signs of corrosion. This may appear as a very slight greenish or whitish discoloration. Clean the contacts as necessary and retest. Next trace the wiring back from the connector to the trailer lights. Carefully check for a loose or corroded ground connection, pinched wires or wires with worn insulation that could be causing a short. Examine the trailer light assemblies for corrosion. Clean or replace worn or corroded components as needed.

We recommend that all connections be treated with an application of dielectric grease, which helps to maintain contact and prevent corrosion. You can use a product such as # 11755 or the equivalent.

I have also included an article on troubleshooting trailer wiring that may be helpful to you.

expert reply by: Adam R

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