Determining Tail Light Wire Functions to Install Curt Harness # C56175 in 1995 Mitsubishi Montero  

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Expert Reply:

Since the wire colors used by vehicle manufacturers are not always consistent, your best option to identify which wires to connect to your Curt Trailer Wiring Harness # C56175 is to use a circuit tester such as # PTW2993 to identify each wire by its function. Wire color alone is not a reliable way to identify function.

With a helper on hand to activate the vehicle lighting functions for you (one by one) apply the grounded circuit tester to each wire at the driver-side taillight assembly to determine what lighting function each carries. You should detect a steady voltage on the running light wire when the Montero lights are on. The wire for the brake light should carry voltage only when the brake pedal is pressed. When the left turn is activated, the wire carrying that signal should carry an intermittent on-and-off signal. The same holds true for the right turn signal wire (which will be on the passenger-side wiring) and which connects to the green wire on the Curt.

Once you know the functions for each vehicle wire you can use the included connectors to splice the wiring into the Curt harness. You will want to pay particular attention to the white ground wire (with ring terminal). This ground wire must be firmly affixed to a clean bare metal surface behind the driver-side taillight assembly, or to an existing grounding point. A solid ground is critical to proper operation of the Curt harness. (Many of the problems encountered with trailer wiring harnesses can be traced to the ground wire so make sure it is very solidly attached to the vehicle.)

Once your harness is installed, we suggest an application of dielectric grease, such as # 11755, on your 4-pole connector. This is also available locally from any auto parts store. This will help prevent the entry of moisture that can over time cause corrosion that can interfere with trailer light functions. It is also a good idea to wrap the quick-splice connectors with electrical tape to protect them from moisture before reinstalling the taillight assemblies.

expert reply by: Adam R

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