Troubleshooting Trailer Left Side Turn Signal Not Working with 2004 Mercury Monterey  

Question:

Expert Reply:

The intermittent function of the left side turn signal on your trailer with the Curt T-Connector Wiring Harness # C56673 installed on does sound like the result of a loose connection or a bad/weak ground. The first thing I recommend doing is using a circuit tester like # PTW2993 to test the 4-Way connector on the Monterey. Test each pin while you have a buddy run through the light functions in the van. If all the pins receive appropriate power with the corresponding light function activated then the issue is actually on the trailer side.

If this is the case then I recommend inspecting the trailer side 4-Way for any debris or corrosion that needs to be cleaned out. Then try and inspect the wiring (you can start with the left side brake/turn signal wire) as far as you can down the length of the trailer, looking for any exposed, damaged, or pinched areas that need to be replaced/repaired. Also check that the trailer grounds are still firmly secured to clean, bare metal surfaces on the trailer. You will do this both for the main harness ground and for the light assemblies themselves.

If when testing the 4-Way on the Monterey the pins did not power appropriately with the lighting functions, then the issue is on the vehicle. Inspect its 4-Way thoroughly for debris/corrosion and try to trace the wiring on the Tekonsha harness, again looking for pinched or exposed sections. Make sure the connections are still securely attached behind the tail lights.

If you still aren't able to locate and resolve the issue, please let me know and we can continue to troubleshoot.

expert reply by: Chris R

0

Paul

6/17/2019

Hi chris r I did check the 4-way flat on the van and it works some of time an some of time it does not work, I clean all of the connections at tail lights look for bad spots in the wiring .did not see anything that looks bad. all of the light work accept the lift hand tail lights and the flasher. I just wondering if the box on the harness is bad .

Reply

Chris R.

6/17/2019

Since the left side trailer light circuits are working some of the time when testing the 4-Way on your Monterey I highly doubt it's an issue with the converter box. If this were the case the problem would be more consistent and would be on both sides. What it sounds like is possibly a bad or weak ground on the harness. Make extra sure that the white wire from the Tekonsha Wiring Harness # 118385 is securely attached to a clean, bare metal surface on the vehicle. It might be worth it to remove the ground and try another nearby location. Please let me know if this does not resolve the issue and we can keep troubleshooting.

Reply