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Old 01-08-2013, 07:45 PM   #1
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No brakes after umbilical problems fixed

Help!

I'm a fairly new Airstreamer and I pinched and cut my umbilical, then fixed it, but my Tekonsha P3 brake controller says trailer isn't connected.

In the morning I am going to troubleshoot the truck and trailer to see what the issue might be but I have no clue about how the trailer brakes work or even where the wiring and any actuators or anything are.

I have a feeling that 12 volts was sent down the brake wire.... Would that damage anything?
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Old 01-08-2013, 07:54 PM   #2
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Couple other notes --

-- I have continuity down the new umbilical to inside the connector on the trailer side.

-- I swapped in an old brake controller that was installed and working in this truck 2 months ago and it also doesn't show the trailer connected. So I don't think the problem is the controller. Hitting the panic button on that controller activates my truck brakes and brake lights.
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Old 01-08-2013, 09:11 PM   #3
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Ok, looks like the brake controller is fine and I am fairly convinced the problem is in the trailer. Most likely I blew something up when I pinched the cable?

I have voltage output all the way to the trailer connector when the brake controller is activated using the panic bar. The P3 controller has a helpful troubleshooting mode and after running some tests I think that I can rule out the controller or anything on the truck side.

That's good in that I can rule out a lot but bad because I have no clue how the trailer brake system works or even where to start troubleshooting that. Is there a controller/actuator bit on the trailer somewhere that I should look at next?

To make matters worse, I can't say for sure if the brakes are original or if they have been changed to something else.

So if anyone can offer advice and a bit of an orientation to where things are I would greatly appreciate it!
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Old 01-08-2013, 10:24 PM   #4
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How many wires in the UCord did you cut? There are at least 6 that are used. Are you sure you connected all the wires correctly?
The brakes on the trailer are actuated by electromagnets in each of the brake assemblies on the trailer axles. I doubt seriously that there was damage to these devices.
Since the brake controller indicates the trailer is not there. My first guess would be that your repair was not successful. Either a bad splice or a connection made where wires may have been crossed.
You should also check for a blown fuse that provides the high current power to the brake controller. Typically this is a 30 amp fuse or circuit breaker. If you happened to have your foot on the brake at the time you pinched the UCord, you may have blown a fuse.
The manual actuator (or panic button as you call it) is used in most cases to make sure the brakes on the trailer are functioning. Sometimes this is difficult to do by stepping on the brake peddle in the TV.
Since you have said you have power at the correct terminal on the Seven pin connector on the TV. I would again suggest that you double check your repair.
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Old 01-08-2013, 11:07 PM   #5
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When you talk about the high current fuse for the brake controller are you talking about my tow vehicle? Or the trailer?

I have poured over fuses in both truck and trailer but maybe less in the trailer so if you are talking about that I will look harder.

On the truck, I have confirmed that the brake controller is putting out voltage on the brake wire all the way through the umbilical to the plug that goes into the trailer. There is a chance I have it wired to the wrong pin, and I keep coming back to that as the most oblivious problem area, but I have checked and pretty sure it is right. I will triple check this in the morning.

I did originally miswire the umbilical to standard 7 way round specs from etrailer's site and pulled my hair out checking fuses and such before realizing that airstreams don't use the standard configuration. I then got my multimeter out and figured out the individual pins for all the lighting circuits. That left me with positive, ground and brakes leftover. Center seems to be positive and top is ground (which seems to match most os the airstream diagrams i found) so brakes were the odd one out.

If all that is correct (and my lights are indeed functioning properly now), I've figured out that the hot positive was previously wired to the brake line in my original wiring attempt. So there was a period when the full 12+ volts was running to the brakes. In reading other posts, apparently you can burn up the magnets if this condition exists for more than 5 minutes. If I burnt up the magnets, would that cause the controller to say not connected? Or would the brakes just be dead?

I agree that the most probable issue is with my wiring and will triple check that in the morning. But what should be my next step after that? Where do the brake wires run.... Directly to the brakes or are there trailer side controllers or fuses to check? I feel like I should check to see where the brake controller voltage stops and right now it seems like it is good all the way to the trailer side of the umbilical.
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Old 01-08-2013, 11:42 PM   #6
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Now that we know you connected the +12 volts directly to the brake wire. There is a possibility that damage was done to the electro magnets.
In reading your last post. I still believe you have a wiring problem. Because, typically the center pin on the 7 pin plug is not used unless you have backup lights and the TV is wired for that.
It would also help, and I may have missed it in your writings, to know what year and model your trailer is, as well as info on the TV.
I have not found a problem with the etrailer wiring info on the net. If you have a vintage trailer. You can be pretty much assured that the wire colors will not match and even the pin out (positioning of the individual wires in the UCord plug) will not match a modern TV.
There are methods of testing the brakes on the trailer using a battery charger. One of those methods is to hold a compass near the wheel and apply voltage to the brake circuit with the battery charger. While this method will indicated there is current flowing thru the electro magnets, it is not as good as raising the tire off the ground, spin the tire, then apply voltage to the brake circuit. The spinning wheel should come to an abrupt stop.
We will keep working with you to help resolve the problem.
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Old 01-08-2013, 11:50 PM   #7
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Let's clarify a couple of things.
Do you have a plug on both ends of a UCord, with a receptacle on the TV and the TT?
Is this trailer new to You?
Is this your first attempt at getting the lights and brakes to work on the trailer?
Did your brakes work, prior to pinching the UCord?
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Old 01-09-2013, 12:09 AM   #8
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Quote:
Originally Posted by TG Twinkie View Post
Let's clarify a couple of things.
Do you have a plug on both ends of a UCord, with a receptacle on the TV and the TT?
Is this trailer new to You?
Is this your first attempt at getting the lights and brakes to work on the trailer?
Did your brakes work, prior to pinching the UCord?
Thanks so much for your help!

Yes, I have two ended umbilical with 7 pin round on trailer side and 7 pin flat on tow vehicle side. Everything has been working fine before the pinch, and it worked fine before I pinched it and fixed it a few weeks ago too. Last time I spliced the old cable but this time I bought a new cable that already had the 7 pin flat on TV side and wired up the round side using the connector from the old cable.

Now, everything seems to be working except for the brakes. Well, I can be 100% sure about four of the 7 pins as I applied power and they lit up various lights on the trailer.

Trailer is new to me about 2 or 3 months ago. I've been using it almost full time since then. It is a 77 excella 500. The truck is a 98 dodge cummins.
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Old 01-09-2013, 12:16 AM   #9
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Quote:
Originally Posted by TG Twinkie View Post
I still believe you have a wiring problem. Because, typically the center pin on the 7 pin plug is not used unless you have backup lights and the TV is wired for that.
My center pin is putting out 12 volts (on the trailer connector) so I am thinking it is the positive/charging line. I wouldn't be surprised if this connector is randomly wired and not to an airstream spec but I am sure is isn't standard matching to etrailer's site. I have found diagrams on the site where airstream has use a center pin for the charging line though where I have seen that it is a slightly different layout to the 7 pins. I will try to attach some that I found.
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Old 01-09-2013, 12:32 AM   #10
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Your trailer may still be wired with the charge line on the center pin. Which is fine as long as you compensate for that on the TV end of the UCord or in your case when you wire up the plug onto the trailer end of the UCord. Since the truck end is pre wired, chances are good that it matches your TV.
Since you have a UCord that has pins that match the trailer (round) and pins that match the TV (flat). It cannot be reversed.
If you know how to use a meter, check the pin to pin continuity of the UCord. Identify which pins on the trailer are for what function. I can guarantee you that if the trailer is wired to the diagram you posted and the TV end if the UCord is wired the same. It will not work with your TV unless you rewire the trailer end to match, function for function. Not by wire colors.
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Old 01-09-2013, 01:00 AM   #11
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I have already done quite a bit of testing with the meter both or voltage and continuity (and will triple check in the morning). I also took a short bit of wire and jumped the pins for the light circuits to the center positive to light those up and confirm them. Then I wired my umbilical to match. All of the lighting is now working properly.

And I also have ensured the brake controller is putting out variable voltage all the way back through the umbilical on what I have deduced is hopefully the appropriate pin on the trailer. I'm just not sure how far into the trailer that brake signaling voltage is going. Is that voltage intercepted or fused within the trailer before it gets put out to the brakes on each wheel? Can I pull a wheel and use my meter to see if the voltage is reaching back there?

It looks like the brake wires may be run within the walls or belly pan though I've read some posts saying people have their brake wires outside the shell. I will have to slide under and look more carefully tomorrow. My instinct is to try to follow the brake controller output voltage as far back as I can and in as many checkpoints as I can to see if it stops somewhere. But if the wires are sealed up in the walls or belly that may not be easy.

I'm also thinking my deduction about which is the brake pin could be wrong, but it definitely has to be one of three pins. As I said before, I think I know two of the three are positive and negative/ground, leaving the last as the brake line. The other 4 i am 100% positive are lighting.
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Old 01-09-2013, 09:10 AM   #12
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Your trouble shooting technics are sound.
In some trailers the brake wire is terminated at a junction box. Not sure about your rig. You can check for voltage at each wheel. On the inside of each tire, there is a back plate to which the brake components are mounted. You will find 2 wires coming out of each back plate. These are the brake wires. You can test for voltage there.
There are 6 wires normally used in trailer wiring.
They are:
Tail/Marker = green
Left Turn/ Brake= red
Right Turn/Brake = brown
Common/Ground = white
Charge Line = Black
Brakes = Blue.
The Black, Blue and White wires are normally larger. 10 Gage.
By using the same method for testing the lights, you can test the brakes on the trailer. Place the jumper between the charge line pin on the trailer and the brake line pin on the trailer. Spin the tire and apply the power with the jumper. If the wheel stops, the brakes are functioning.
Once you have determined which pin on the trailer is the brake pin and the brakes are working. Wire the plug on the UCord accordingly.
You can roll one set of tires onto blocks, which will raise the tires of the opposite axle off the ground for testing purposes. In the maintenance of the brake system on the trailer, periodic adjustment of the brakes is required. There are numerous videos on YouTube explaining how this is done. This may be a good time to check and adjust the brakes while you have the tires off the ground.
Keep us posted on your progress.
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Old 01-09-2013, 10:50 AM   #13
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Oh boy - I must have had a premonition about this as I recently had been researching lifting wheels off the ground to educate myself should the need arise. And 2 days ago I bought a 2x8 to make some blocks specifically for that purpose. I may have to run to town for a lug wrench as I have not found one for this trailer. Could it be stowed under the pan with the spare? I do see a spare down there on my rig.

I'm actually boondocking at Lake Mead but I think I can get the wheels off here. I was hoping to hit the road today ahead of a cold front coming in but that may not be possible. Maybe I'll triple check my wiring before I start taking wheels off.

Quote:
Originally Posted by TG Twinkie View Post
In some trailers the brake wire is terminated at a junction box.
Is this different than the 7 way access box on the inside front wall of the trailer? In that location, I do see what I believe are the brake lines coming in and being spliced together. There are a couple places where they come together so it isn't exactly clear to me what is going on yet. If there is another potential junction please give me an idea where that might me so I can search.

On wire colors, mine seem to be close to what you have posted and what I've read about for lighting. But I believe my positive/charging is blue as I have +12 on that. I do see that sometimes airstream used that, as in the diagram I posted. My belief is that my brake lines are orange - either that way from airstream or from rewiring from a previous owner. I have seen that airstream has used yellow sometimes so it seems like someone could have been following something like that.

Do you know more details on how the magical single wire brake line works? I'm assuming the brake controller is looking for a closed circuit to know that the trailer is connected, correct? Can fried magnets cause an open circuit? Anything else?

Anything with the ground? Does the trailer/brake system ground need to be tied together with the ground on the tow vehicle for it to function? I wonder if the vehicles are effectively grounded together at the moment since they are not hitched and if that could be an issue. I know the trailer wiring should do that bit maybe it isn't.
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Old 01-09-2013, 11:49 AM   #14
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Quick update - I have confirmed my brake line pin is the one I am using. It is indeed orange and it comes inside the cabin and makes some funny junctions into a two conductor cable running down the belly pan to the brakes. I am attaching a pic. The blue line in the pic seems to be running to the breakaway switch. I'm not sure if the orange splits into BOTH of the conductors in the two conductor cable or what... Some of the wiring is hidden inside the wall.

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Putting my meter probes on the hot positive and the brake pins gives me a reading of just like .2 volts or something. Should I be getting 12 volts on that? I do get 12 when I do the same thing on lighting pins.

My next step is to probe along these wires to find how far the brake controller output voltage is going. I'm starting to think it is going to be fried magnets. How can I test those individually? And can I find replacement parts locally at a trailer mechanic or napa?
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