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Trailer locking up when backing


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I have a 2001 Ford F-150 with the towing package, which includes both the round 7 pin plug and the flat 4 pin that comes factory. I towed my cousin's boat down to San Antonio and when I tried to back the trailer in to load the boat, the brakes locked up. My cousin pulls the boat with a Dodge truck with the same plug that I was using. All of the lights worked when hooked up to my truck and no fuses are blown. I ended up having to stick a nickel in the sliding part of the hitch to prevent the brakes from locking up.

What do I need to do to fix this problem? I probably wont be towing his boat many times, but I am just curious what is different in my plug?

The trailer is an Extreme.

Edited by jcaksume
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yes the actuator can cause the brakes to lock up in reverse but the 4 pin plug should over ride that. there is a little button that u are suppose to push to make sure they don't lock up...its under the actuator and should have a yellow sticker that says something about it on the side.but if that doesn't work you can always unplug the harness and plug just the far right pin into one of the other plugs on your truck...then turn your lights on, on your truck and it will engage your reverse override on the trailer..might have something unplugged on the backside of your harness or something

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There are different round connectors that you can purchase. You need to ensure that you are using a 5 pin as opposed to a 4 pin on the round connector. The fifth pin sends the signal from the reverse lights to disenguage the trailer brakes. If you are not using the round adapter and need to use the 4 flat adapter on the truck to the 5 flat on the trailer you can do this however if you are backing up, unplug the flat adapter reverse it, allowing only the three brass connections on the truck side to be connected to the trailer and this will disenguage your breaks when trying to back up. I had to go to a trailer shop to find the 7 pin round to 5 pin flat adapter. You can find the 7 round to 4 pin flats almost anywhere however the 7 -5 are difficult to sometimes find.

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just for a test.... as mentioned in the previous post

take the 4 pin and reverse it... that way the last pin has a connection. turn on your parking lights/lights and see if it will release.

Usually, that is the answer. my trailer has a 5 pin and my S10 has a 4 pin so I have to do that until I rewire. My trailblazer has a 5 pin so I am fine with that vehicle.

Ebay rules!

Edited by martho
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I wasn't using the flat 4 harness. I was plugging the round 7 plug from the trailer into the round 7 plug on my truck. All of the lights on the trailer were working correctly, so thats what confused us.

My cousin never has to push any buttons on the slide actuator to back it up. I may just need to check all of the pins and see if they have power when I'm in reverse.

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I wasn't using the flat 4 harness. I was plugging the round 7 plug from the trailer into the round 7 plug on my truck. All of the lights on the trailer were working correctly, so thats what confused us.

My cousin never has to push any buttons on the slide actuator to back it up. I may just need to check all of the pins and see if they have power when I'm in reverse.

This might be a stupid question but there are round 7 pin adapters that are only wired for 4 pin,5 or 6 pin, they still have the 7 slots their just not wired for seven, Make sure you have the correct one.

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Our trailer has a flat five pin plug. We need an adaptor which goes from the five on the trailer to the seven on the truck. The 5th pin is for the back up light on the truck which is accessed from the 7 pin on the truck. This electrically cuts out the brake when backing up. I'm not sure if your's is the same, but I can't think of another way to cut out the brakes besides what you are already doing.

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After doing a little searching on the site, it sounds like its common for the soleniod to have a grounding problem, and my hitch ball may have been a little rusty. Here is the link for someone else that was having similar problems. http://www.themalibucrew.com/forums/index....se+trailer+lock

Hopefully this is the problem, but I would think it would happen with his truck too. I'll just have to do more investigation.

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I believe that this is a problem specifically with the Ford pin pattern. I had this same problem when my brother in law used his F150 to back up the boat after I had pulled it to our camping area with the motorhome. The trailer brakes would lock up every time he would try to back up the boat. We got around it eventually by using a metal insert that came with the trailer to prevent the trailer brakes from engaging. We just inserted the plug when he was using his rig to trailer the boat from the campsite to the launch and back.

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I'd check ALL your fuses as well. Do you have reverse lights on your trailer?

That's the fuse that needs to be hot and there's a particular fuse just for the trailer in your Ford.

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Also, make sure the trucks wiring harness is getting power. In Ford's, there is an additional relay (usually in the glovebox) that needs to be installed under the hood for the backup wire to have power.

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I had the same problem with my 2001 Expedition. Ford did not run a relay for the reverse signal to lockout the brakes on a bunch of the 2001 models. If you want to get it fixed the dealer can install the relay for about $25 bucks, or you can just flip the connector and turn on your lights.

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I had the same problem with my 2001 Expedition. Ford did not run a relay for the reverse signal to lockout the brakes on a bunch of the 2001 models. If you want to get it fixed the dealer can install the relay for about $25 bucks, or you can just flip the connector and turn on your lights.

I had the same problem with my 2003 F150. The relay was in the glove box....a 45 second fix.

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what i did to correct this problem on my '00 expedition (didn't know about the relay), is i ran a wire from the backup lights to the corresponding pin on the 7 pin round connector.

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After doing a little searching on the site, it sounds like its common for the soleniod to have a grounding problem, and my hitch ball may have been a little rusty. Here is the link for someone else that was having similar problems. http://www.themalibucrew.com/forums/index....se+trailer+lock

Hopefully this is the problem, but I would think it would happen with his truck too. I'll just have to do more investigation.

That other post is the one I created I was having issues sometimes backing but not all the time, I have a Dodge 03 and the reverse light worked coming out of the truck on the 7 pin connector, I took it to a trailer shop and they said that the actuater is grounded through the truck and if it wasn't getting a good ground it would cause the problem, they suggested grounding the body of the actuator to the trailer directly, I have had no problems since then. If you have power coming out of the truck when in reverse then this would be my next suggestion.

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I had this issue - it was a 5 amp fuse - check to see if your trailer light fuse is burned out - think it cost me $.79

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