Hi Folks!

2012 F250 XLT. Troubleshooting trailer brakes not working, I started with the truck. Using a simple plug-in tester at the trailer plug, I found all other outputs working, but the trailer brake output blinking on the tester LED for that output. It blinks at a consistent repeat interval every several seconds. Did some research and read this is supposed to be an indication of a fault in the trailer brake wiring or functions.

Spent some time learning the wiring and checked for opens or shorts, found and checked all related fuses and relays and all were fine. I know the ground to the trailer plug on the truck is OK as I checked the output voltage on the +12 power output terminal also using the ground terminal in the plug and read full voltage.

With everything else looking normal, I was thinking maybe the brake controller itself was failing. I then rigged a little clamp (small vise grip) to hold the brake controller manually ON for continuous output and checked the output, with the plug-in tester, at the trailer outlet plug. To my surprise, it all looked great. The trailer brake output LED and both brake light LEDs were fully lit. Then I let the brake controller go back to idle and jammed a stick on the brake pedal to hold it ON. Back at the trailer plug I, again, found all 3 of the correct LEDs fully lit. When activated through the trailer brake controller, the output appears to be working and normal.

So....now I am wondering why I see that blinking trailer brake output when no braking is activated. Is that actually a normal state when no trailer brake output action is being done? Or, is it still some fault being indicated even when everything appears to be working normally when the trailer brakes output is applied? I've never had to dig into this system before, so I'm now confused by that blinking/pulsing trailer brake output.

Anyone else ever seen this? Thanks for any feedback!

 

The brake controller will not work unless the truck is moving around 5 to 7 mph but the manual slide will work setting still. So I would say your trucks system is working as designed.
Denny

 

Yep, I don't think you have a problem.

 

Sounds like the issue isn't the truck.

If you're still having brake issues on the trailer, a quick test is to plug it in to a different truck and see if they work. In my experience, if they DON'T work with the other truck, it's a wiring/ground issue on the trailer, if they DO work it's an issue with the plug on the trailer.

If it's a ground/wiring issue on the trailer, clean all grounds, maybe even run dedicated ground wires for the brakes (they're kind of important). That should clear things up.

If it's a plug issue, look at the plug you've got. There are cheap $5 plugs, and they're garbage - they'll really only work with older, more forgiving receptacles on older trucks, newer trucks with factory receptacles don't like them. Pollak makes most OEM receptacles, and their plugs work pretty well, but they're a bit pricier.

I have had good luck with the 'spring style' plugs. It's what came stock on our travel trailer, and when I was having issues with my flatbed, switching it to a 'spring style' plug fixed the issues.

These are the style I'm referring to:

 

I think that blinking is the truck sending a very small signal to "sense" the precense of the trailer. I would ignore that for now. If you have anotehr trailer with "known good" brakes that would be helpful. If you ahve another truck to pull this trailer with, that's also a decent place to start.

 

Thanks guys!

I was beginning to think that consistent blinking or pulsing on the test plug might be some kind of sensing signal. I did note that blinking didn't seem to be nearly as bright as the light emitted from that same test LED when the brake controller, manual control was engaged. With all your feedback, I'm satisfied that my issue is on the trailer side and I'll get after checking that side of the system!

 

The truck systems are pretty reliable, but the "smart" nature of them makes it harder to troubleshoot. I think you are on the right track to troubleshoot trailer side next.