Weird trailer brake problem
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Junior User
Joined: Feb 2008
Posts: 87
Likes: 0
From: Snohomish, WA
Weird trailer brake problem
I am having a very strange problem with the electric brakes on my car hauler trailer. I'm towing with an F150 with the factory towing package, using a Prodigy controller and the F150 specific cable.
Not every time, but about 75% of the time, if I park the truck and turn it off, when I start it back up, the trailer brakes will be locked up solid. Usually at this point, unplugging the trailer plug and re-plugging it will make them unlock. Sometimes it takes a couple of tries to get them to unlock.
I can't find any shorts in the wiring, and once I get them unlocked, they operate perfectly until the next time I shut the truck off.
Anybody ever seen anything like this?
Not every time, but about 75% of the time, if I park the truck and turn it off, when I start it back up, the trailer brakes will be locked up solid. Usually at this point, unplugging the trailer plug and re-plugging it will make them unlock. Sometimes it takes a couple of tries to get them to unlock.
I can't find any shorts in the wiring, and once I get them unlocked, they operate perfectly until the next time I shut the truck off.
Anybody ever seen anything like this?
Posting Guru
Joined: Jun 2004
Posts: 2,433
Likes: 1
From: Apex, N.C.
Have you checked all of your grounds good. Sounds like something on the trailer is improperly grounded and is back feeding into the brake circuit. Also do not depend on the physical connection of the coupler/ball for a ground.
Thread Starter
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Junior User
Joined: Feb 2008
Posts: 87
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From: Snohomish, WA
I'm not sure I understand, what should I be depending on? I'm using all factory wiring. Is the factory installed wiring harness not properly grounded? Do I need to add something else?
Hotshot
Joined: Oct 2005
Posts: 12,237
Likes: 22
From: Florida
I'd also check your emergency break away switch...perhaps it has an intermitent in it and by connecting/disconnecting the main 7 wire plug...you are putting some noise on the ground or something...
Just a thought as it is one item that is designed to intentionally LOCK your trailer brakes...
Joe.
Just a thought as it is one item that is designed to intentionally LOCK your trailer brakes...
Joe.
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Junior User
Joined: Feb 2008
Posts: 87
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From: Snohomish, WA
It is definitely just the regular electric brakes with magnets, not hydraulic.
And I definitely am not starting out with my foot on the brake.
I'll check out the breakaway switch and see if there is anything loose there. It seems to work correctly - if you pull out the breakaway cable the brakes come on, and go off when you push it back in.
I've checked everything out with a multimeter, and it seems to be wired correctly, and the grounds seem to be good.
And I definitely am not starting out with my foot on the brake.
I'll check out the breakaway switch and see if there is anything loose there. It seems to work correctly - if you pull out the breakaway cable the brakes come on, and go off when you push it back in.
I've checked everything out with a multimeter, and it seems to be wired correctly, and the grounds seem to be good.
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Hotshot
Joined: Oct 2002
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From: The Big, Oregon
What I meant was starting the engine with your foot on the brake- Maybe the controller is freaking out seeing a drop in available power then it coming back on while getting a brake signal.
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Junior User
Joined: Feb 2008
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From: Snohomish, WA
I don't normally have my foot on the brake when cranking, but do have to put it on the brake to shift into gear.
I also have a brand new very beefy battery (Sears Diehard Platinum P2).
I also have a brand new very beefy battery (Sears Diehard Platinum P2).
FTE Legend
Joined: Jul 2005
Posts: 65,938
Likes: 1,432
From: Millersville, MD
If you haven't found the probleem yet, I'd re-visit the advise to insure your truck/trailer is grounded thru the electrical connector. Unhitch the truck from the trailer, then using a multimeter check continuity between the trailer ground and the truck ground (frame to frame). You should have it...it shows the plug is correctly wired for a ground and you do NOT depend on the hitch to provide the ground thru the hitch. The ohms should show close to 0 ohms if using a digital meter or if using an analog meter, the needle should deflect back to (or near) 0.
Thread Starter
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Junior User
Joined: Feb 2008
Posts: 87
Likes: 0
From: Snohomish, WA
If you haven't found the probleem yet, I'd re-visit the advise to insure your truck/trailer is grounded thru the electrical connector. Unhitch the truck from the trailer, then using a multimeter check continuity between the trailer ground and the truck ground (frame to frame). You should have it...it shows the plug is correctly wired for a ground and you do NOT depend on the hitch to provide the ground thru the hitch. The ohms should show close to 0 ohms if using a digital meter or if using an analog meter, the needle should deflect back to (or near) 0.
Fleet Mechanic
Joined: Nov 2003
Posts: 1,372
Likes: 14
From: West Cornwall, CT
If the trailer check out OK. it sounds like your trailer brakes are being actuated by the controller when they should not be.
Either you have a brake applied signal going to the controller or perhaps the controller is faulty.
If you can temporarily swap out the controller you could better isolate the exact problem.
Lou Braun
Either you have a brake applied signal going to the controller or perhaps the controller is faulty.
If you can temporarily swap out the controller you could better isolate the exact problem.
Lou Braun
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Junior User
Joined: Feb 2008
Posts: 87
Likes: 0
From: Snohomish, WA
Not yet. I'm planning to do a little more troubleshooting this weekend, and if I am not able to narrow down the problem, I will probably do that.
Thanks everyone!
Thanks everyone!