Lights, no lights, lights

[cathy liebchen]

It’s not the trailer if it does the same thing on a different trailer

 

[Monster5601]

Not sure about Ford but past experiences with trailer lighting issues have been isolated to grounding, 7-way plug contacts, and the vehicle's fuse or relay controlling the trailer circuit. Many manufacturers use both a fuse and a relay to provide trailer circuit control.

For those looking for a 7-way tester that includes trailer brake controller testing, this is the one I use. It is amazing how many friends I've made with this device at campgrounds.

https://smile.amazon.com/Electric-Dynamic-Simulation-Circuit-Testing/dp/B073FJ5NVL/ref=sr_1_5?crid=17YDFLHDYAS05&keywords=trailer+brake+tester&qid=1662626951&sprefix=trailer+brake+tester%2Caps%2C86&sr=8-5

 

[ljjhouser]

It was not long ago that checking trailer brake/turn/marker lights was simple and straightforward. But today on the newer trucks, it seems the dealer must program the computer to make the brake controller work. I guess that is because the truck now "recognizes" when the trailer is connected, and my truck measures the length to determine the distance needed for the "Lane Change" warning. A trouble light probe and common sense might not work well.

 

[BleedingOrange]

Lights, no lights, lights, to me means an intermittent open, in a poor connection. Sometimes, getting back to the basics in troubleshooting helps isolate a problem. Determine if it is a problem with the truck, or trailer. That gets you half way to finding the problem, in either the truck, or the trailer side of the equation.

 

[RustyA]

His title is a little misleading compared to his description of the concern. He has running lights but no stop or turn lights with truck hooked to two different trailers. The lights don't come or go, they just don't work at all for stop and turn. My money is blown fuses for rh and lh turn trailer feed which are combined to make trailer brake circuit.