Lights, no lights, lights

[RSKY]

I have a 2014 Ford F150 with trailer package. The lights on my tandem axle trailer are not working correctly. I have been hooking it up and pulling it out of it's parking spot. Then I will kill the motor and go check the lights. The truck lights stay on for about a minute after the engine is killed and the trailer lights would be on. Or I would turn the light switch on and check the lights and they will be on. But the brake lights and turn signals do not work. So today I hooked to the SIL's new trailer and it is the same way. His trailer lights came on with the truck lights but no brake lights or turn signals.

Any ideas?

RSKY

 

[WM75Guy]

One of the best trailer tools I bought was a checker for the truck plugs, $12.89 on Amazon. It's Works for 7 and 4 pin sockets. Also my 2017 GMC
HD has a separate fuse for each trailer function.

Amazon.com: ABN 7 Blade 4-Way Flat Circuit Tester - Trailer Testers Electricity Wire Circuits Connector Testing for 12v Vehicles : Automotive

Buy ABN 7 Blade 4-Way Flat Circuit Tester - Trailer Testers Electricity Wire Circuits Connector Testing for 12v Vehicles: Electrical System Tools - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

 

[grsthegreat]

Newer model trucks generally have separate fuses that operate trailer lights than the circuits that run truck lights. Also, trailer grounds are major problems. I also use a plug in analyzing tool when working on trailers. Major time saver.

 

[RustyA]

Should be a separate fuse panel for your towing circuits under the hood. Check fuses for rh stop/turn, and lh stop/turn first. Exact location and numbers of fuse cavity in owner's manual. That's where I would start

 

[RSKY]

OK, will check that out. Thanks guys.

RSKY

 

[duffer]

Funny you should post this. I just had my F150 at the dealer for the exact same problem. Even though my truck is newer than yours, it could still be the same issue.

There is a sensing module that "talks to the computer" for the trailer. This lets you "program" the trailer, adjust brakes, etc based on the type and size of the trailer. Well it also controls the signal and brake lights. And in my case the stupid auto start/stop switch and sensor.

My module is located under the dash just to the left of the steering column. Check to see if you have 2-3 wires with plugs going into a module. Make sure they are all plugged in. I had one wire that was unplugged. Once it was reconnected all was well with the world....except for the stupid auto start/stop switch is active again.

Since your truck is a 2014 you don't have the auto start/stop "feature" (I don't think). But you could still have a module that controls the signals and brakes for a trailer hookup. Worth a look.

I agree you may have blown a fuse, but if the truck signals and brakes work, then it many not be a fuse.

 

[BleedingOrange]

Use a 12V test light, and a jumper clip. Use a small bunji cord to keep the cover open while testing. Connect one end of the jumper clip to the ground inside your 7 pin male plug, and the other end to the test light. Use the pin-out diagram on the cover of your 7 pin plug to find which pin should have +12 volts when activating that function, i.e., left turn, right turn etc. and brake, running lights. Scratch the surface of each pin while checking to make sure you get thru the oxidation. That will prove if you are getting power to each required pin, or not. If yes, with the power off, take a small flat bed screwdriver, and gently spready all 7male pins, and also scrape each pin gently to get some of the oxidation off, to help make a better connection once you attach the female end. If no power when checking, it has to be a problem going back towards the fuses, either a faulty wire, or fuses. To confirm the trailer end isn,t a problem, try connecting it to someone elses truck, that has the same plug wiring arrangement as yours.

 

[grsthegreat]

He said he hooked it up to another new trailer and no change.

 

[BleedingOrange]

Maybe the male pins on his truck are not making a good enough connection to the female plug. If he goes by the instructions I gave him, he can find out if it is the fuses, the wiring to the plug, or the male pins in the plug causing the problem.

 

[RSKY]

I have a lot to check on the truck and trailer today. Well first I have to retrieve the trailer from my daughter's house. Will let everybody know what I find.

Once again, thanks to all who took time to respond to my post. TBN and the people who inhabit it are the best!

RSKY

 

[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.