Troubleshooting Turn Signals Going Out When Brakes Are Pressed After 4-way Connector Is Installed

Question:

I installed this kit in my 2009 Grand Marquis but I am having trouble with the function. When I use my turn signal L or R and hit the brakes the turn signal stops working. This happens even when the fuse is pulled from the power cable. What do I have crossed?

asked by: Greg G

Expert Reply:

Since the turn signals go out when applying the brakes in our 2009 Mercury Grand Marquis I recommend using a circuit tester like # PTW2993 on the green and yellow wires when you have the turn signal on and the brakes are being applied.

If you are getting power on the green wire or yellow wire on your wiring but the turn signals are not working that means there is a grounding issue on the trailer side.

I recommend double checking the main ground on the tongue of the trailer that it is connected to the clean corrosion free metal, and that all of the grounds for the lights are connected to clean corrosion free metal. If your trailer has an aluminum frame or tilt bed you may need to run jumper wires from each light to the main ground.

If you are not getting power on the green or yellow wire then you will need to double check the connections of the harness you installed to make sure they are not loose, and double check the main ground for the harness.

I included a link to a helpful article on wiring for you to take a look at.

expert reply by: Samuel C