Trailer brake question
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Elder User
Joined: Jun 2006
Posts: 764
Likes: 1
From: Gulfport/Biloxi, MS
Trailer brake question
I recently bought a trailer with brakes and the guy told me he had towed with it the week before and the brakes worked fine. My truck does have a brake controller but ive never used it so I dont know. Nothing ever lights up on it or moves. I plugged the trailer into the truck and all the lights and all worked, but the brakes were locked up. As soon as I unplugged the trailer the brakes released. I dont have a clue why the brakes would engage as soon as I plugged them in. A friend told me that he has seen multiple superduties do the same thing and that the truck must be wired different than standard. Any ideas?
Logistics Pro
Joined: Jun 2005
Posts: 4,243
Likes: 16
From: AZ
To find your problem requires a two step process:
1) Take a test light or voltmeter. Have a friend step on the brake of your truck. Find the wire in your trailer plug that is hot. Now you have the truck wire that energizes the trailer brakes.
2) Energize each plug of your trailer plug (on the trailer) until the trailer brakes lockup. Now you know the trailer plug wire the brakes get their electricity from.
Now, you need to match up the truck wire that energizes the trailer brakes with the trailer plug wire the brakes get their electricity from. You need to find out why your brake controller is not working...you will have no control of your brakes (in other words, it will either be completely off or completely on) without the controller working. The controller should light when you step on the brake...
1) Take a test light or voltmeter. Have a friend step on the brake of your truck. Find the wire in your trailer plug that is hot. Now you have the truck wire that energizes the trailer brakes.
2) Energize each plug of your trailer plug (on the trailer) until the trailer brakes lockup. Now you know the trailer plug wire the brakes get their electricity from.
Now, you need to match up the truck wire that energizes the trailer brakes with the trailer plug wire the brakes get their electricity from. You need to find out why your brake controller is not working...you will have no control of your brakes (in other words, it will either be completely off or completely on) without the controller working. The controller should light when you step on the brake...
Posting Guru
Joined: Mar 2004
Posts: 1,307
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From: MARYLAND
is it the 7 round RV style plug? Or you using an adapter to go from 6 round to 7 round Rv?
The problem is that the black and blue wires inside the adapter are reversed causing the brakes to stay on.
I've had this happen before.
The problem is that the black and blue wires inside the adapter are reversed causing the brakes to stay on.
I've had this happen before.
Logistics Pro
Joined: Jun 2005
Posts: 4,243
Likes: 16
From: AZ
Originally Posted by Help I M Stuck
is it the 7 round RV style plug? Or you using an adapter to go from 6 round to 7 round Rv?
The problem is that the black and blue wires inside the adapter are reversed causing the brakes to stay on.
I've had this happen before.
The problem is that the black and blue wires inside the adapter are reversed causing the brakes to stay on.
I've had this happen before.
Elder User
Joined: Mar 2003
Posts: 699
Likes: 0
From: northern Michigan
Other place I would look is the pigtail adaptor harness that is wired to the brake controller. Ford uses a prewired plug under the dash, but the brake controller manufacturers provide an adaptor harnes to go between it and the brake control. Who ever wired it up may have crossed some wires.
Thread Starter
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Elder User
Joined: Jun 2006
Posts: 764
Likes: 1
From: Gulfport/Biloxi, MS
Originally Posted by Help I M Stuck
is it the 7 round RV style plug? Or you using an adapter to go from 6 round to 7 round Rv?
The problem is that the black and blue wires inside the adapter are reversed causing the brakes to stay on.
I've had this happen before.
The problem is that the black and blue wires inside the adapter are reversed causing the brakes to stay on.
I've had this happen before.
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Posting Guru
Joined: Mar 2004
Posts: 1,307
Likes: 0
From: MARYLAND
Originally Posted by Futuresweets-10
I did indeed use an adapter to go from 6 to 7 pin, so I guess thats my prob. Should the trailer brake controller light up even when I dont have a trailer plugged in or just when the trailer is plugged in? Also, I shouldnt have a problem fixing it as I worked in 12v electronics for years, but does anyone know what wires hook up to the brake controller? Like how many should their be and what is their function? Thanks
WHITE-Ground
BLUE-goes to rear of truck for brake wire to trailer
RED-gets conncected to brake pedal wire that has 12v when pedal is pressed.
On that adapter ..take the screws out and cut the black wire going to the trailer side..take the blue wire off of trailer side pin and put it where the black wire was on trailer side of conncector..then it will work and brakes wont lock up.
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Thread Starter
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Elder User
Joined: Jun 2006
Posts: 764
Likes: 1
From: Gulfport/Biloxi, MS
Originally Posted by Help I M Stuck
BLACK-12V+
WHITE-Ground
BLUE-goes to rear of truck for brake wire to trailer
RED-gets conncected to brake pedal wire that has 12v when pedal is pressed.
On that adapter ..take the screws out and cut the black wire going to the trailer side..take the blue wire off of trailer side pin and put it where the black wire was on trailer side of conncector..then it will work and brakes wont lock up.
WHITE-Ground
BLUE-goes to rear of truck for brake wire to trailer
RED-gets conncected to brake pedal wire that has 12v when pedal is pressed.
On that adapter ..take the screws out and cut the black wire going to the trailer side..take the blue wire off of trailer side pin and put it where the black wire was on trailer side of conncector..then it will work and brakes wont lock up.
Posting Guru
Joined: Mar 2004
Posts: 1,307
Likes: 0
From: MARYLAND
yeah..cutting the old style plug off the tailer and putting a new 7 round rv style on them is what i plan on doing one day when i get around to it. Too many other things to do..not enough time in the day..day late..dollar short thing going on here for now. 
Lead Driver
Joined: Jul 2003
Posts: 7,406
Likes: 52
From: Wheatland, Mo
6 pins, at least for what I have seen are still used for smaller campers like popups. I use the 7pin RV type for everything I tow, but on occasion, pull a trailer with the 6pin, or the 4 pin flat. I just carry an adapter that has both on it. Works great since I have a friend that I pull his old gooseneck that has a 6 pin about every other week when he needs another trailer for hay loads.
Freshman User
Joined: Aug 2007
Posts: 47
Likes: 0
simply put. you have the brake wire and the aux wire crossed in one or the other. you can change either one you want around to match up. on the topside of the black plastic part of the 6 pin plug (not the adapter) it will be labeled RT-right turn, LT left turn, TM trailer marker (running lights), GD- ground, S- COULD BE "STOP" OR COULD BE WIRED FOR THE AUX. The center prong is normally used for tthe AUX. Anyway just swap the wire in the center and the wire in the S terminal. 2 Minutes you DONE.
