Questions regarding my truck and a trailer I just bought...

Discussion in 'Towing & Trailer Tech' started by wmkess, Feb 4, 2013.

  1. wmkess

    wmkess Rockstar 100 Posts

    Hey guys: I just bought a used stock trailer from a friend I go to church with. It is a 1988 WW bumper pull with a double axle . The livestock area is 14' x 5' x 6'; total dimensions are about 17' x 7 1/2' x 8'. My questions on this trailer are in regards to the brakes. It appears to have electric trailer brakes, however, the trailer wiring harness connector is just the standard 4 pin. The brakes didn't appear to work when I was stopping the few times I have pulled it so far (Yes, I know they shouldn't work due to the 4 pin connector but this leads to my question). The wires that run to the brake drums appear to lead back to the front of the trailer and appear to be spliced into the current harness. I was wondering if people will connect the electric brakes to the brake light signal to try to achieve non-variable trailer braking as opposed to variable braking from a brake controller? I have no clue and sounds unsafe but where I'm from, I'm sure its been tried. Maybe the brake light signal is enough to apply, say 33% of the trailer brakes and aid some in slowing down? Again no clue if people try this but I was just wondering. I plan to haul goats or horses (2 max) with no trips longer than 15 min and no steep grades so braking isn't a huge deal right now but I would like to get them functional for future endeavors as well as just to keep the brakes active so they stay working properly and for resale purposes.

    I was also wondering about my truck's brake controller interface, if it even has one. It is a 2005 Silverado 1500 Z71 with the 5.3L, 4.10 gears, and transmission cooler. The gearing and cooler indicate it is intended to be used to tow so I was hoping it had a quick connect under the dash so that I could buy a controller and plug it in and be ready to messy wiring. Anyone got an idea on that?

    Thanks in advance for any responses. I'll look at the trailer wiring more closely this week in hopes of getting a better idea about how it is wired and why it only has the 4-pin harness and update the thread.
  2. steved

    steved Former Member

    Sounds like the PO rewired the trailer and did not include the brake wiring. That's a typical thing that's done when the tow vehicle isn't set up correctly (even though its not the correct or safe way to do it).

    You will need to install a new plug (like a 7-way RV, probably have one if you have the tow package)...and find the wiring for the trailer brakes (the brakes and brake lights are two different circuits). There will be two wires, a positive and negative for each wheel that will get tied together at the plug, I don't think the actual pucks in the brake system are polarity sensitive.

    As for the controller wiring, I don't know. Some trucks equipped with a trailer tow package have the wiring under the dash, but I'm relatively new to the GMs.

    E_HILLMAN Member 1 Year

    You sure you don't have hydraulic brakes on the trailer (the controller is in the tounge of the trailer) The wires going to the 4 pt are normally in that case just to pick up the reverse light to disengage the hydraulic brakes so they don't grab when you are backing up.
    If they are hydraulic brakes and not working look for a screw or plug on top of the frame that might hold brake fluid for the actuator. If the fluid is good then take the wheels off and look at the brakes. Are they rusted up? ARe they covered in grease from a over used bearing buddy thus the grease keeps them from grabbing?

    Just some thoughts from past experiences I have had. ;)

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    PS, Got a pic you can post?
  4. steved

    steved Former Member

    I never even gave the hydraulic brake thing a thought...they aren't that common around my parts. Good catch.
  5. wmkess

    wmkess Rockstar 100 Posts

    I appreciate the response steved. I'm sure the trailer was rewired previously for broader connectivity on more trucks. The friend I bought it from is actually a full-time cattle farmer. His family, employees, and he all drive half tons when doing their daily chores due cost as well as due to less weight when making frequent trips through muddy pastures. The trailer I bought from them was one of theirs they primarily used for moving problem cows around, usually just 1 or 2 at a time. Being that they have much larger trailers they haul large amounts of cattle on, I doubt they ever used this one for any serious on-road or high speed transportation. I'll use this as an opportunity to go ahead and rewire the trailer and do necessary work on the brakes to get them working properly.

    Also, if you don't mind, I have a follow up question for you...when I rewire it with a 7 blade plug to fit my truck, can I have it split to also have the old 4 pin plug? It would be nice to have both in case there is a situation where someone else uses it or I have to use another truck for some reason and the 7 blade plug isn't on the other vehicle.

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    I guess you could be right. There actually is a small piece by the jack that could be just that. I kind of just assumed it was the ground location.

    I don't have a pic of it right now, but I can snap a couple when I get home and post them.
  6. steved

    steved Former Member

    I see no reason (other than the obvious) that you can't wire in a standard 4-way flat in addition to the 7-way RV. Obviously this will render the brake circuit inoperative, but I can understand why you may want to do this.

    I would have a 4-way flat on hand when you do the 7-way RV, and when you hook the stop/turn/tail and ground up to the 7-way, just slip the corresponding wire from the 4-way into the 7-way's terminal and tighten...tape up the wires out of the 7-way (so the 4-way doesn't pull the wires out of the connector). That would eliminate splicing into your new wiring any more than you have to.

    I would highly suggest solder and heat shrink all your connections, makes them secure.
  7. Crawdaddy

    Crawdaddy All hail the Mad King!! Staff Member 5+ Years 1000 Posts Platinum Contributor

    Hooking electric brakes up to the brake light circuit is extremely bad form. Doing that means there is no ramp up of braking current, and all current for the brakes is consumed by the brake light circuit which could be upwards of 40 amps. That much power flowing through a brake light circuit can easily blow a fuse or start a fire. Put a proper 7-way on and install a brake controller on your truck. Also install a battery and breakaway switch on it so the brakes will slow the trailer down if it gets away from the truck.
  8. wmkess

    wmkess Rockstar 100 Posts

    Thanks for all of the responses guys. You all have been a big help.

    I self determined it has electric brakes but went ahead and included a pic I took I took yesterday when I got home from work.

    I bought a new 7 blade connector for the trailer today and in the near future I plan to wire it in as well a 4 pin connector. I will check the wheel bearings and do what's needed to them and hopefully the brakes on it are still functional and can at least be rebuilt versus replacing the whole assembly.


    E_HILLMAN Member 1 Year

    Yep, definitely electric

    Why not instead of splicing in a 4 wire into your new wiring just buy a 7pin to 4 pin adapter and keep it with the trailer. That way if someone has 4 pin they just pop the adapter on.


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    Hmm, the one I linked above might be backwards but I'm sure there has to be one, and if not make your own adapter. It HAS to be better than leaving another splice in that is just flopping around getting corroded.

    Just IMO.
  10. Crawdaddy

    Crawdaddy All hail the Mad King!! Staff Member 5+ Years 1000 Posts Platinum Contributor

    I'd just put the 7-way on the trailer right and be done with it. If someone needs to tow the trailer and they do not have a 7-way and brake controller, they shouldn't be towing it in the first place. Trailers that have trailer brakes have them for a reason: because they're needed. Sure, when empty it's lighter, but that doesn't excuse the need for the brakes.

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