I recently replaced the factory bed with a flat bed. I used one of the factory trailer plugs and bought another that fit better in the flatbed design.
all the lights work on the bed,,turn, back up and running lights.

However, when I plug in a trailer, the truck does not seem to detect it. I can manually activate the trailer brake controller , which gives me the sign for "no trailer".

Any suggestions?,, thanks h

 

Which plug did you replace, the 7 pin or the 4 pin? Might want to make sure you are properly grounded and also make sure that however you replaced the plug that you were looking at position and not only color of the wires. Do any of the trailer lights work?

 

The brake controller uses the 7 pin connector. The way it detects the trailer is by having a load on the brake wire relative to the ground. Basically, the brake signal from the brake controller (12 VDC when the brakes are applied) is floating without the resistance of the magnet (brake activator) to ground. So, the first thing you need to do is measure the voltage from the 7 pin connector to truck ground using a voltmeter set to 20 VDC, do this with the brakes applied. If it's there, then connect the trailer and measure at one of the wheels, there are 2 wires going to each wheel and one of them is the brake signal.

 

Thanks for the reply's.
I didn't have to do any Major "rewire" as the female plugs on the bed matched up to the factory wiring harness, just plugged them in.


All the other trailer light's work fine, no other problems. I will check the ground .

 

If everything else worked then just trace the brake wire from the factory harness to the 7 pin plug on the new bed - see if they even bothered to run a wire there for it.

 

Do the trailer brakes work when connected to other trailers? Or when a different truck is hooked up to your trailer?
Just trying to eliminate other possibilities for ya

 

It seems that I have all the wires connected properly. Ground is good.

I checked the output with the voltmeter between the ground pole and the trailer brake pole on the 7 pin connector. With the trailer brake applied, the output is below 1 volt,,, goes between .5 and .8,, back to .3 then up again.
Then I checked it at one of the trailer hubs, same reading.
The truck still signals there is no trailer hooked up.
I hooked the truck to a different trailer, it signaled the trailer was hooked up, and the controller signaled there was output. My next step is to check the output on the second(working) trailer to see what the output is.
All of your input has been utilized and is appreciated. Any more ideas will be used.
Confused and dazed with no brakes. Maybe I should start drinking and then go work on them. h

 

You need to see 12 VDC at the connector or at the trailer brake input. If you did not set the voltmeter correctly that may explain your readings, or the brake controller is not wired correctly. Good idea to check the voltages with a different trailer.