Towing wires harness & trailer brake nightmare

[brando77]

I recently received help from another member on another topic, so I thought I'd try this again.

I have this very frustrating problem with my expy and towing.

I have no trailer brakes (Activator II says "." when trailer is connected). I have brake lights, tail lights and turn signals.

I did have a blown fuse for trailer brakes and trailer battery +. I replaced those and they worked fine. Then the next day we were leaving on a trip, while I was leaving the parking lot every time I barely touch the brakes, the trailer brakes engaged fully and instantly. I checked the manual activation slider on the Activator II and when i pushed it over EVERY light in my expy (including head lights) quickly (2 seconds) drained to nothing then popped back on. I then noticed I had no brake lights on anything (including expy) so trip was cancelled (kids cried).

Did some digging and found Brake light switch had burned off its contacts. Replace that, and now have no connection light on controller. So I went and checked every fuse and every connector and every relay. all good. I unplugged trailer and re-plugged and got gibberish on the brake controller with foot on brake and err when using slider. I tested the 7 way harness and found that the trailer brakes connection had 23.7 vdc?

how can you get 24vdc in a 12v system? I'm guessing the control is bad, since the trailer brakes wire comes directly form the controller. its not the trailer because any trailer i hook up does the same thing, I guessing I cant get warranty replace because of how I mounted it.... drilled 2 wholes in casing (no i did not hit anything in the controller with the drill because I took the case off and the screws aren't long enough)


any ideas before i take it in shop and spend hundreds?

 

[bedrck46]

prints

 

[bedrck46]

How did you wire the Brake Controller??

You may want to just leave power to the controller and with the blue wire disconnected to the trailer connector check to see what voltage the controller is putting out

 

[brando77]

I just used the factory harness under the dash with harness that goes to brake controller.... and without the trailer hooked up and checking the output on the bue wire it fluctuatues from 17-24 volts

 

[bedrck46]

I just went and checked my Primus IQ and the output was 12.6 VDC You may have either a bad controller or you meter isn't reading correctly.

 

[Mediamonkey11]

Have you gone into deep water recently and the trailer receptacle shorted out your brake switch? Trace back and try to see what has happened recently, check for good grounds, and check to see if anything has hit wiring underneath the truck. Don't know much about controllers but if it's putting out that voltage when brakes aren't applied it sounds bad, it's what took it out that has me wondering.

 

[bedrck46]

suggest that you follow the instructions for bench testing the controller that are on the installation instructions.

Do the following without the engine running so that you are checking battery voltage

Have everything connected except for a trailer and test for voltage at the connector on the rear of the controller. Check between the blue and white wires and manually activate the controller and you should have approx. 12.6VDC

If you get approx. 12.6 VDC then disconnect the connector from the back of the controller and jumper the black and blue wire and then check the voltage at the 7 pin connector to see if it reads approx. 12.6 VDC.

If at anytime you have more than the 12.6 volts I would say the controller is bad.

Then post the results

 

[brando77]

Sorry... Been working a lot. I can attest for the 14 years this truck has not been in water. Plus in rains here like 3 times in the winter and that's it.

I bought a tekonsha p3 today. They said they would take it bake if it gets messed up. Before that though I'm gonna try what bedrck46 said and post. I'm also gonna tripple check everything. I'm pretty close to just scrapping the whole built in controller harness and just re-wire the whole thing.

 

[billycuth]

I have an odd, and possibly related situation with my brake lights.

I didn't notice this until I was following my wife who was driving the Expy over the weekend.

Her brake lights illuminate when she first touches her brakes. Then they go out. Occasionally they might flicker while she is slowing down (already hit the brakes and saw an initial flash of the lights, then they go out). Finally, when the vehicle comes to a complete stop, the lights illuminate and stay on.

I do recall that when I would hit the brakes on the expy, you could hear an audible clicking noise underneath the dash. That sound is no longer heard. So I am definitely thinking that it could be the switch. But perhaps it is a relay? Maybe it is both?

I cannot pinpoint when this started. But I can tell you that I do tow with my expy so I do have a brake controller wired in using the factory harness. I ran the wires from the plug that I installed on the back bumper and spliced them into the brake controller wiring. I do not obviously keep the controller plugged in when I am not towing.

My wife accidentally backed her car into her mothers car in our driveway a few months ago and it did bend the crap out of the metal bracket that I mounted the plug with. It did not appear that any wiring was damaged after I bent it back. I didn't notice anything abnormal since that happened. But this weekend I definitely noticed an issue with the brake lights.

Thinking I will replace both my brake light switch and a relay. Any idea which relay i'd want to replace?

I just realized that this thread is for a 2000. Mine it 2006. I did a search to get here. Any help would be appreciated. Thanks!

 

[brando77]

It's your brake light switch... Like $14 at autozone.... Had the same problem...

Sent from my PC36100 using Tapatalk 2

 

[billycuth]

thanks! Ordered it from Rock Auto... Autozone wants $45

Stoplight Switch | 2006 Ford Expedition 4WD 8 Cylinders 5 5.4L EFI SOHC | AutoZone.com