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Trailer Lights - Issues with 7 pin to 4 pin

Recommended Posts

Hey guys,

My 05 CTT came with factory hitch and wiring, it also has a brake controller mounted under the dash (installed at P dealer by previous owner). My trailer has no brakes and uses a 4 pin light plug so I purchased a 7 pin to 4 pin adapter locally.

When I plug the trailer lights in I only get a continuously flickering light from the passenger side trailer light. Nothing else lights up.

I also have a small "trailer light tester" which has 3 LED's on it one is labeled TAIL the others LT and RT. When I plug this tester in I get all three LEDs flickering continuously. I am guessing this tester does not work properly because it uses LEDs and does not create enough resistance.

I have tried searching quite a bit and there are a lot of trailer light threads but I'm still not sure what I should try next to trouble shoot this. I have tested the trailer lights on there own and they are working but when I plug them into the truck I have no luck.

I have attached a photo of my 7 to 4 adapter as well as the tester.

Thanks in advance for any suggestions!


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