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TriCityLawnCareLLC
03-07-2012, 05:56 PM
This will probably get moved to the mechanic section but thought i'd try to get some of you guys (who don't visit that section) to see this and maybe help me out.

I bought a used trailer last year. tandem axle 3,500 each axle. It's a Big Tex trailer, year 2003. It came with electric brakes on the rear axle only. When i bought the trailer a year ago i also bought a Reese Pilot control box for the cab. I wired up the box correctly, even inserted the 40amp fuse in stud #1. im getting 10volts on the trailer brakes at the rear of my truck. But the box keeps telling me that there is no trailer hooked up, so my only guess is that there is not a closed circuit somewhere, correct? The box is putting out roughly 10volts when i squeeze the trigger, but it doesn't register any numbers on the display, only a little dot showing that it's hooked up.

ive tested all plugs (truck and trailer) with ohm meter and they're good. ive gone all the way back to the brakes on the trailer. there' a black wire and a white wire (black:power white:ground) that run down the left-hand side (drivers side) of the trailer, once they reach the rear axle they get spliced with power going to the brakes on the drivers side then power and ground run from that splice across the trailer to the other brake.

I cut the wires right where they were spliced, hit my brake pedal and tested, i'm getting 9.5volts of power. So i've deducted that I've got power to the brakes. OH, i forgot to mention, when i first started playing tinkering around today, i found out that something somewhere is crossed because the brakes were activated with no pedal or controller box. Then once i hit the brakes pedal the trailer brakes let up (freed up). So for a second it was reversed somehow, brakes applied = no trailer brakes and no brakes applies=trailer brake. But after i re-tested everything and hooked it all back up the problem went away. ???

THINGS I KNOW:
1. there are not power issues on the truck (2005 gmc sierra z71)
2. Both trailer and truck plugs are fine
3. Have good power and good ground all the way back to the trailer brake

My Questions:
1. Why does the reese pilot box show no trailer connected, even before i cut into the wires?
2. How do i know if the electro magnet is good or bad?
3. there are two wires that go into the magnent, they are both green, how do i tel which is positive and which is ground, or does it even matter?
4. Was it a possible ground issue that cause my brake to be applied even though i wasn't applying the brakes?
5. Where do i go from here to figure this problem out? Thanks guy.

OH and from the rust on the inside of the brake hub, the brake shoes aren't engaging, only the magnent is. So tomorrow i'm going to pull the whole brake unit off and tear it apart and beat the rust off and lube it and get them function i hope. I hope someone reads this and can help out. Thanks.:usflag:

TriCityLawnCareLLC
03-07-2012, 05:57 PM
don't know why that dumb smily face got put in above

tyler_mott85
03-07-2012, 06:06 PM
I've experienced and heard of problems with two different methods of wiring the plugs and when you go to wire in the brake controller when it comes to the truck to trailer connection that's where the wire gets crossed and you get brakes all the time. Specifically its only the two wires that control the brakes, obviously. This is the only thing I could think to explore with my limited knowledge of trailer brakes. I do not know anything about that specific controller so I cannot help there.

I can also add a tidbit of info that trailer brakes do not self adjust like brakes on trucks/cars so you have to physically get a brake spoon and adjust the brakes as they wear down so even if you do not get any noticeable braking from the brakes they may be out of adjustment.

good luck!

Richard Martin
03-07-2012, 07:00 PM
I agree. It sounds like the truck and trailer are not wired the same.

You can test the function of the trailer brakes with a 12 volt battery. Just jack the trailer up and apply 12 v to the blue wire. The brakes should keep the wheel from turning. Even if there is a problem with the brakes you should hear the magnet humming. The magnet wiring is not color coded. Either side to ground with the other connecting to blue.

I do a lot of trailer wiring repairs and this is how I wire all of the 6 and 7 pins up.

TriCityLawnCareLLC
03-07-2012, 09:41 PM
Richard,

I'm glad you've got experience in this!! After posting, i went out and fiddled around some more and was able to get 12v on the black wire (on the trailer) at the actual drum where before i only got 9.5, now obviously the black wire wasn't hooked up to the brakes, i cut the wire to test.

Bare with me as i try to figure this out. So on my trailer i have a blue wire that comes from the trailer plug (6 hole trailer plug which i plug into and adapter with 6 holes that plugs into my truck which has 7 point) and goes into the break-away box but i have no blue wire that runs all the way back to the trailer brakes, only black and white wires. My understanding is that the black should provide power to the magnet while the white acts as a ground.

Now regarding the break away box, something is also amiss because i'm not getting any volts whatsoever at the battery. The battery is also dead, but i was under the impression that the battery was for the break-away only.

also,Should the control box in the cab be putting out 12v? I left it hooked up but i unplugged the blue wire and then squeezed the trigger and I was only getting like 6-7 volts.

So, i thought maybe i had it figured out, but now i feel like i'm back at square one.
The magnet was working enough earlier to slow the wheel down to where i was barely able to turn it, but the actual shoes didn't even move, i need to free them up. I really appreciate the help and hopefully we can figure this out. I'm still perplexed as to why the control box isn't working? So many questions

dhardin53
03-07-2012, 10:26 PM
You need of a new breakaway battery. The low or no battert is giving you the bad hook up signal.

TriCityLawnCareLLC
03-07-2012, 10:31 PM
I also failed to mention that i only get 12v back on the black wire at the trailer brakes when i hit the pedal. The controller box, when applied does nothing

dhardin53
03-07-2012, 10:45 PM
If you replace the battery all will work fine, The breakaway battery is only in effect if and when the connection to the truck and or control box is broken.

The hand brake on the control box will not let you lock the trailer brakes for safety reason. The pedal will give off 10 to 12v for maximum braking power.

dhardin53
03-07-2012, 11:02 PM
Some years ago when I was traveling with our band. The bass player was driving the truck pulling the equipment trailer. He had the truck on cruse control and trying to get comfortable he rested is knee agents the control box brake. So the trailer was trying to stop (7v) and the truck drooped out of over drive and went to racing to keep the speed stable. Scared the bajesues out all of us. But there was nothing wrong after he hit the brake pedal.

Richard Martin
03-08-2012, 03:32 AM
Bare with me as i try to figure this out. So on my trailer i have a blue wire that comes from the trailer plug (6 hole trailer plug which i plug into and adapter with 6 holes that plugs into my truck which has 7 point) and goes into the break-away box but i have no blue wire that runs all the way back to the trailer brakes, only black and white wires. My understanding is that the black should provide power to the magnet while the white acts as a ground.

Now regarding the break away box, something is also amiss because i'm not getting any volts whatsoever at the battery. The battery is also dead, but i was under the impression that the battery was for the break-away only.

Okay. We're going to fix your wiring one problem at a time. You have so much buggered up that it's near impossible to tell what's going on.

The place to start is at the truck plug. Believe it or not, not all 7 way plugs are wired the same, even when they come from the factory.

Then we're going to jump to the trailer and identify which wire does which function.

Then we're going to put a new 7 pin plug (dirt cheap) on the trailer. A lot of problems start when using adapters. I have no idea how the adapter is wired. There are no universal rules or laws governing the wiring so everybody does pretty much what they want to.

Once we have the truck and trailer wired the same then we can work on getting everything working on the trailer.

This is the exact way I would fix your trailer if it was sitting in my driveway.

Like I said, start at the truck. Print out the 7 pin diagram I posted above. When you're looking at the diagrams you're look at the pin side. The wires would go in the back of the diagram if it were a plug.

One by one test the pins on the truck. You may need a helper to activate the truck brakes so you can be sure that brake power is going to pin number 2 as shown in the diagram. Test all 6 pins that go around the outside and make sure they do what the diagram says. The center 7 pin may have 12v constant, may work with the backup lights or it may not have anything. That is an optional pin and you can do with it as you like.

If the pins don't do what the diagram says, make a note of it on the diagram that you printed out. We will have to make sure the trailer end is wired the same way. That or you can dig into the wiring on the truck and correct it. Since you've never done this before I think it's far easier just to wire the trailer to match the truck. Chances are good though that the truck is wired correctly.

I'll be in and out all day so I'll check on your progress here at Lawnsite. Once you complete a section we'll move to the next section.

TriCityLawnCareLLC
03-08-2012, 04:05 AM
Thank you gentlemen. Richard, I will get started on it today and I'll let you know what i find out tonight. Thanks again, i appreciate you're help!

TriCityLawnCareLLC
03-08-2012, 04:10 AM
Richard, As i mentioned I'll start with the trailer plug, i'll re-wire it to fit a 7 pin plug and i'll go from there. I'll print out the wiring diagram for my truck and wire the trailer plug accordingly.

TriCityLawnCareLLC
03-08-2012, 04:15 AM
This is how my 7 way plug on my truck is wired. So instead of re-wiring the truck, buy a 7 way plug for the trailer and wire it to match the truck, correct?

Richard Martin
03-08-2012, 04:31 AM
Yes. Match the trailer to the truck. Just remember, the trailer plug will be the opposite of the truck socket. That picture you posted is what the trailer plug should look like from the wired side. That is the same wiring that I posted.

TriCityLawnCareLLC
03-08-2012, 10:43 AM
Richard, here is one photo, going to upload another one real quick then i'll explain.

TriCityLawnCareLLC
03-08-2012, 10:49 AM
The other photo isn't coming through . Basically I've cut the old plug off and I've also disconnected the breakaway system( I'll reattach later). I Have 6 wires on the trailer plug, red white blue brown yellow green. Turns out red is my 12v power wire instead of black. As you see in the photo, what goes where? Previously the red(12v power) went into the battery charger for the break away, blue connected to black which went back to trailer brakes along with white. Well as I said I want to bypass te breakaway portion for now, so my question is, where does the ref (12v) get hooked up to now that there is no breakaway battery charger?
Posted via Mobile Device

TriCityLawnCareLLC
03-08-2012, 02:53 PM
Update: So far today I have(in order):
1.)Cut old 6 round plug off of trailer. Wired trailer into a 7 way plug.
2.)Disconnected the break-away box and battery.
3.)Hooked everything up and the controller box still showed that there was no trailer connected
4.)Re-checked voltage, everywhere. All day yesterday and today I was only getting 6.5v at the rear of truck and the rear of trailer. So i checked the box and it was only putting out 6.5v, AT THE BOX!! even when i would adjust the voltage it read a steady 6.5v without fluctuating.
5.)Got stumped as to where to even go next so i just started working on the drums
6.) Got drum shoes taken off. Between fluid-film, sand paper and some files i got all the rust knocked loose and put everything back together.
7.)Put drum back on and had to take off to adjust the shoes
8.) hooked the black and white wires back up to the magnet (just twisted together for testing purposes)
9.) Had my father hit the brake pedal and the brakes locked up TIGHT!!
10.)Tried the controller box and same thing, brakes locked up TIGHT!!
11.) Controller box is now showing that trailer is hooked up and that it's putting out 12v. When i try both the pedal and controller box i am now getting 12v at rear of truck and front of trailer.

So, that's good new for me!! But I don't see what we did different to get anything to work. My only guess is, when we put the brakes back together, i just wanted to test them so i wired in the 12v power supply wire to the brakes. They obviously locked up. After that is when i retried my controller box. So i don't know if the 12v power supply did it or if freeing up the brakes did it, I have no clue?

Now, my same question remains, where do i hook up the red 12v power supply that was once hooked up to the brake-away box?

Richard Martin
03-08-2012, 03:41 PM
Now, my same question remains, where do i hook up the red 12v power supply that was once hooked up to the brake-away box?

Since you no longer have a use for the 12v you don't need to have it at the trailer. You can leave the wire, just don't hook it up to the 7 pin plug.

Richard Martin
03-08-2012, 03:44 PM
And if you want to use it in the future connect it to the #4 terminal.

TriCityLawnCareLLC
03-08-2012, 03:51 PM
Thanks Richard. I already have it hooked up. I'm going to play around with the breakaway box and see if i can get it working. If not I'll just cap of the 12volt. Do you have any idea as to why it just started working, out of the blue?

Richard Martin
03-08-2012, 05:13 PM
Thanks Richard. I already have it hooked up. I'm going to play around with the breakaway box and see if i can get it working. If not I'll just cap of the 12volt. Do you have any idea as to why it just started working, out of the blue?

Perhaps one of your old connections was bad. When you're pulling and tugging on wires it can tighten things up sometimes.

TriCityLawnCareLLC
03-09-2012, 09:20 AM
Thanks Richard. I've been out there since 5:30 this morning working on the other hub. I've got it all cleaned up and working with one exception/question.

How tight should i adjust the brakes? the right side spins but i can hear rubbing, the left side spins with no rubbing. But when the brakes are applies, i cannot move the left side by hand. The right side i can move by hand with much force.

When I pull it empty with max volts i feel a the brakes kick in but not very strong. I'm no expert but I would figure that i should get a bit more resistance? Let me know what you think.

TriCityLawnCareLLC
03-09-2012, 09:35 AM
I'm going back out there and take everything apart again to make sure ive got that right side hub on center. Whenever i put it in reverse two things happen:

1.) The controller box shows that there is no trailer connected, but as soon as i put it in drive it shows that the trailer is connected again

2.) as i go slowly in reverse it feels like one of the brakes is hung up, but i jacked the end of the trailer up and and both wheel spun fairly ok. I still feel like i'm getting resistance as i back up...

Richard Martin
03-09-2012, 09:36 AM
You should just barely hear the shoes rubbing.

Most electric trailer brakes are marginal when they are working correctly. Manufacturers should be required by law to put brakes on both axles in a tandem axle setup. The only time I've seen trailer brakes that were worth a darn was when both axles had brakes.

There could be a few reasons for inconsistent braking between the two sides. You have to make sure all of the connections are 100%. You have to make sure the grounds are 100%. One of the magnets (or both) may be getting weak. One or both magnets may be wearing out. The brake drums may need to be resurfaced.

TriCityLawnCareLLC
03-09-2012, 09:41 AM
Any idea as to why the brake control box shows "no trailer connected" symbol when in reverse?

Richard Martin
03-09-2012, 09:47 AM
I'm going back out there and take everything apart again to make sure ive got that right side hub on center. Whenever i put it in reverse two things happen:

1.) The controller box shows that there is no trailer connected, but as soon as i put it in drive it shows that the trailer is connected again

2.) as i go slowly in reverse it feels like one of the brakes is hung up, but i jacked the end of the trailer up and and both wheel spun fairly ok. I still feel like i'm getting resistance as i back up...

What brand and model brake controller do you have?

Have you connected another trailer with brakes to the truck to ensure that this is a trailer problem? It sounds like a truck problem.

TriCityLawnCareLLC
03-09-2012, 09:51 AM
It's a Reese Pilot.

I don't know of anyone else that has a trailer with brakes. I'll go back through the truck...

TriCityLawnCareLLC
03-09-2012, 10:10 AM
Well, i just went out and jacked the trailer up, had my wife put it in reverse (with wheels chalked) and just putting it in reverse locks up the wheels. Sound like some wires are crossed somewhere somehow. I'm not sure if it's my truck or the control box.

Richard Martin
03-09-2012, 10:18 AM
I'm thinking that the controller has gone bad, although I would feel better about saying that if you hooked another trailer up.

Richard Martin
03-09-2012, 10:28 AM
Someone may have also done something bizarre to the wiring in the truck. It is entirely possible to wire it so that 12v is applied to the trailer brakes when the truck is put in reverse. It would be a simple matter of slicing into the backup light circuit. What happens when the truck is in park or neutral?

Get a volt meter and test the voltage at the truck trailer socket on pin 2 when the truck is in reverse. It should be minimal or 0.

TriCityLawnCareLLC
03-09-2012, 10:29 AM
Will do . I'll let you know
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dboyd351
03-09-2012, 06:32 PM
Some controllers have an electrically wired cutout to disconnect the brakes when you go to back up, so that may be why you see a difference when you put it in reverse.
Also, not sure about your brake wiring, but most "12V" systems in trucks, including trailer lights, are meant to operate on 12-13 volts, not 7 or 9 or 10. If you are getting substantially less than 12 volts that may be part of your problem. To get an idea of what the voltage should ideally be coming from the battery try hooking the tester directly to the 2 battery terminals. On a well charged battery, you should see somewhere between 12.6 and 13.2 volts.