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Old 08-28-2018, 09:07 PM   #1
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Unhappy electric brake wiring

Conducted my first road test today on an 87 T1850 tandem axle Satellite with electric brakes. Found only one brake was working. After crawling underneath
I found a broken wire and some poorly made electrical connections. I also identified a wiring concern. The electric brakes for the front axle are wired in series (daisy chained). The brakes for the rear axle are wired independently in parallel. I suspect that series wiring is wrong and that all the brakes should be wired independently. This makes more sense to me. If they are wired in series and one fails, it breaks the circuit for all. Can one of you repair gurus confirm my thinking?
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Old 08-29-2018, 09:09 AM   #2
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Because total resistance is the sum of a parallel circuit it allows the controller to know if there is an issue with one brake because the resistance will be lower than expected. If they were series wired one bad connection would kill all four brakes being parallel 3 would still work.
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Old 08-30-2018, 08:45 AM   #3
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Thanks for confirming my assessment of the wiring Mainah. I just wanted to make sure there was NOT some logical explanation for how the brakes are currently wired now that escapes my imagination. Obviously someone made a connection error long before I purchased the unit. Glad I found it and have now ordered new electromagnets for all 4 wheels.
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Old 08-30-2018, 04:46 PM   #4
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Hint, do not pull the break away cord to check brake operation unless all 4 are of the ground and you can do it really fast. Likely as not it will cook the switch and maybe some wiring. Have a friend apply the TV brakes to test them whilst plugged in much safer.
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Old 09-01-2018, 10:10 AM   #5
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thanks for the tip Mainah
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Old 09-01-2018, 08:38 PM   #6
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I agree, something is messed up if you have a true series connection of the front 2 brake coils. All 4 brake coils are to be wired in parallel. Meaning each brake coils has it's own brake hot (+) and ground (-).

Are you meaning they ran the hot wire on the front axle to the first coil, then out of the first coil and over to the other side coil wire. Then out of the other side coil and went to ground? That would be a series connection.

Hook them all up in parallel and it will work a lot better. Also old wiring run inside the axle tube can become brittle, chaff off leaving exposed wires and after each bump/bounce short out to the axle tube. A classic textbook brake fault on an older camper.

If yours is brittle on the ends where it comes out and you can see it, odds are high it is brittle inside.

Running a new 2 wire cable on the back side of the axle tube (so things do not hit the wire while towing forward) outside is one approach to correcting this. The other is to run a new 2 wire cable down each side of the camper and go to each brake coil, then jump to the rear axle again in parallel. Then there is no crossing over. If you do this, run the DC (-) negative from the 7 wire cord all the way to the brake coil. Rusted frame grounds on a brake circuit is another classic textbook way brake faults occur.

Hope this helps

John
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Old 09-01-2018, 08:49 PM   #7
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Quote:
Originally Posted by mainah View Post
Hint, do not pull the break away cord to check brake operation unless all 4 are of the ground and you can do it really fast. Likely as not it will cook the switch and maybe some wiring. Have a friend apply the TV brakes to test them whilst plugged in much safer.
Hi Mainah,

Expand on what you are saying here. I'm not understanding the context of your concern. Please explain more. If the camper is wired "correctly", pulling the breakaway switch will not overload the wiring. It will drain the battery big time if left on a long time as you have the ability to be pulling 12 amps on a 4 coil setup non stop.

Now that said if you mean with his front axle wired in series and then pulling the break away, the resistance on the front axle would be higher (2 coils in series = higher ohms) which should be lower current.

What am I missing?

Thanks

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Old 09-02-2018, 09:50 AM   #8
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thanks for the wiring tip JohnB. Replacing all the wiring is a good idea. All the connectors show signs of water infiltration & rust.
You understood correctly... the output of the left coil fed the input of the right coil on the front axle then back to the connector ground. Definitely series wired, which didnt make sense to me. Somewhat glad I had a problem and forced me to check the wiring. Have new magnets and will be wiring all in parallel today.

Re: the breakaway switch, after the road test with little braking, I jacked up the trailer and quickly used the breakaway switch to identify which brakes werent working, then did individual ohms testing. 3 of them appeared to have open circuits. I would think these coils have the ability to take a full 12v power input. Am I wrong?
Any good thoughts re: waterproof connections?
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Old 09-02-2018, 10:07 AM   #9
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Yeah the coils will take 12 volts the wiring won't take the load of the magnets for very long though! Because 2 magnets wired in series would not produce the resistance the controller expected it should have had a code it also will half the voltage to two magnets reducing their effectiveness. They do make wire nuts with a sealant inside the big box should have them. With 12 volts applied the brakes should lockup hard there will be a little bit of play before they lock up because of the mechanical parts turn the wheel in the direction of travel they don't work real well going backwards.
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Old 09-02-2018, 11:22 AM   #10
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Quote:
Originally Posted by dmil123 View Post

Re: the breakaway switch, after the road test with little braking, I jacked up the trailer and quickly used the breakaway switch to identify which brakes werent working, then did individual ohms testing. 3 of them appeared to have open circuits. I would think these coils have the ability to take a full 12v power input. Am I wrong?
Any good thoughts re: waterproof connections?
Each brake coil when new has target of 3.2 ohms of resistance. Not a lot. Do not know what readings you were seeing.

And yes, each coil can handle a full 12.7 volts and will draw 3 amps at that full voltage.

Watertight connections, Sunline used a insulated crimp splice and then pumped silicone in the exposed end. Here is a pic. Not saying it is the best but better then many.



When I redid mine, I soldered the connection, heat shrink tubed the connection then 3M 33 premium electrical tape.


The wire size, here bigger is better. The minimum on the main line from the front to the axle is 12 awg on trailer your length according to Dexter Axle. No. 10 awg will be better. Do not know what size yours has as original.

This may give you some ideas. I did this back in 2009 and it is still working as good as it did then. Independent Brake Wire Feed Upgrade

Since then, we did my son's trailer with running a dual marine tinned wire (no 10 awg) down each side of the camper and jump to the wheel still with no 10 awg. This eliminates the crossover and I consider it better then the way I did mine in 2009 with single wire. But both are a major upgrade in lack of voltage drop and getting all the current to the coil. You can even run 2 single wires down each side, just the cable helps bundled it.

This is the cable if interested. There are other brands too and places to get it. https://www.amazon.com/Duplex-Tinned...YCB&th=1&psc=1

While you are doing the wiring upgrade, consider a new breakaway switch if your looks very old. They are only recommended to be used for 5 years by the manufacturers. Many times they never get pulled and the pin freezes up inside to never pull out when needed or the switch rusts up. I pull mine and silicone spray the O ring seal on the pull pin at the start of each season. This helps cut down on the pin binding issue and the O ring cracking.

When you have the camper wired and sized correctly, the wire should not melt when full power is applied. That said, old trailers may have a lot of wiring issues from too small a wire gage, corroded up connections to brittle insulation etc.

Hope this helps

John
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Old 09-02-2018, 07:14 PM   #11
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You don't want to do that John the full current exceeds the rating of the breakaway switch and the original wires at 12 volt they draw some pretty hefty current. Some of the wiring is #16 including the wire in the axle tube so at 3.2 ohms that's 15 amps not including voltage drop.The plan is to stop the trailer during break way not long term so frankly they don't care if the switch etc. burns up it just slams on the brakes as tight as they will go long enough to stop the trailer.
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Old 09-02-2018, 10:43 PM   #12
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Quote:
Originally Posted by mainah View Post
You don't want to do that John the full current exceeds the rating of the breakaway switch and the original wires at 12 volt they draw some pretty hefty current. Some of the wiring is #16 including the wire in the axle tube so at 3.2 ohms that's 15 amps not including voltage drop.The plan is to stop the trailer during break way not long term so frankly they don't care if the switch etc. burns up it just slams on the brakes as tight as they will go long enough to stop the trailer.
Hi Mainah,

I hear you I'm sure you may have seen what you are talking about. If the older trailer is wired too underrated, this can be a problem. And I 110% agree, do not pull the breakaway switch and leave it out a long time, long being many minutes, 2 to 3 or more etc. I really cannot think of a need that long even in a testing phase.

For the folks following along caution needs to be used in understanding this if someone is trying this on an older trailer. I cannot speak to all the older trailers, as I do not know all of those components.

I have tested this on the year 2000 and newer Sunlines with the Bargman breakaway switch. I always questioned if that wire that feeds the switch could ever pass full current. So I tested it.

The normal Bargmen breakaway switch is rated at 15 amps as I found on the side of the switch. This one linked below. It has about 3 ft leads of 14 awg wire. So there is often 6 feet of 14 awg wire between the battery and the point it taps into the brake wire circuit. Bargman - Breakaway Switch

My thought was that limiting wire size could add enough resistance to not allow full current to pass to the brake coils. So I measured the current on my trailer. I have no. 10 Awg wire all the way to every brake coil just there is this switch in the mix. My camper is also 32 ft long and longer then many. This is not the normal setup, a more enhanced one with the heavier wire.

I will do this test over in the next day or so to get the actual numbers again with pics, but that switch will not pass full current as theory says it should be. On 12.7 volts of a fully charged battery, and using 3.2 ohms of brake coil resistance, this would be 12.7/3.2 = 3.96 amps per coil. However Dexter rates the coil at 3.0 amps. 4 coils at 3 amps is 12 amps using the Dexter rating. Or 15.84 amps on 4 coils using Ohms law calulation.

I have a DC clamp on meter and use this as a troubleshooting tool on trailer brakes. I first test for a dead short with an ohmmeter on the 7 wire plug pins. If I pass that I do not have a short, I then Clamp on the breakaway wire, pull the pin and measure the current. Takes all of 30 seconds to a minute at most to even do it over several times. This gives you a quick read if all brake coils are even hooked up and actually pulling close to the right current. On my camper I recall getting about 12 to maybe 13 amps. I will repeat this again and report back with the exact numbers.

On some campers I tested with failed brake coils I get really low current. How low depends on failed they are. Some can have brake coils not hooked up at all, broken wire and others with the coil shot or open circuit, the breakaway switch all froze up and not closing. Poor wiring, rusted grounds undersized wire the list goes on. Point is, I have never seen 15 amps on a 4 wheel setup. A 6 wheel setup could/should have more than 15 amps.

Mainah, have you seen 15 amps or higher on a 4 wheel setup? Or did some of the older breakaway switches have less ratings? If there is a dead short, the wire is going to become the fuse where ever it is the smallest. The brake controller may handle the shorted wire better than the breakaway switch. One should test for a dead short before pulling the pin.

Hope this helps the cause.

John
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Old 09-03-2018, 07:12 AM   #13
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Yes recently a friends trailer where he drove off with everything disconnected except the breakaway cable. Damaged wiring and a very melted switch. The switch completely failed so the damage was not as bad as it could have been because it interrupted the circuit. I cooked one of my own switches a year or so ago it lasted about a minute. I had all 4 wheels off the ground and by the time I checked the last one the switch was toast.
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Old 09-03-2018, 07:55 AM   #14
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I will check the rating on my '87 Satellite Bergman breakaway and post later today. I dont know if there is a way to tell if the switch is original but I did notice the o ring seal on the plunger had failed. So I need to disconnect the battery and replace that. I have only been using the breakaway for 5 to 10 secs at a time for a quick test when spinning the wheels off the ground... no issues thus far, but the cautions are duly noted. I will use the tow vehicle electronic brake set at a low voltage in the future. Thanks.
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Old 09-03-2018, 07:58 AM   #15
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just a PS. One of the old electromagnets tested at 3.2 ohms and 2.8 amps after it was removed. It was showing an open circuit when installed so I suspect a broken wire somewhere to the unit.
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Old 09-03-2018, 09:43 AM   #16
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Quote:
Originally Posted by mainah View Post
Yes recently a friends trailer where he drove off with everything disconnected except the breakaway cable. Damaged wiring and a very melted switch. The switch completely failed so the damage was not as bad as it could have been because it interrupted the circuit. I cooked one of my own switches a year or so ago it lasted about a minute. I had all 4 wheels off the ground and by the time I checked the last one the switch was toast.
Thank you for reporting back. Much appreciated.

This is very concerning. That breakaway switch is a state and maybe even federal mandated switch to prevent a run away trailer in the even of a decoupling. How in the world can the trailer industry cheap out this bad on something so simple to overcome.

By chance do you know any of the specifics of the switch? brand, model number and ideally age of the switch?

I need to do some more digging into this and report back.

Thanks

John
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Old 09-03-2018, 04:55 PM   #17
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Well I can say this the entire affair will last long enough to stop the camper and if anything is burnt up it will be the least of your worries! When that switch is closed it's far more voltage than the brakes will ever see in normal breaking I mean real tire smoking stopping so I guess that's all the laws require. I can say this they say do not use as parking brake with the replacement switches and I'm thinking they don't really care about a dead battery! Just for giggles I just googled burnt up/melted break away switches yep there are loads of hits.
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Old 09-04-2018, 09:53 PM   #18
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I checked the Bargman breakaway installed on my '87 Satellite. No ratings or model number that could be readily seen. Just a warning that pulling the plunger could damage the brake system!!! New electromagnetic brakes are installed with new wiring along the backside of the axles. Unfortunately, the magnet retainer clips supplied in the kit dont fit the brake levers to which the magnets mount. Hopefully, the correct ones are on order and I can test when they are installed. And the hits just keep on coming!!!
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Old 09-04-2018, 10:28 PM   #19
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A suggestion, change the breakaway switch to a new one.

So far in my info dig on this, the manufactures recommend changing them every 5 years. And some 3 to 5 years....
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Old 09-06-2018, 08:44 PM   #20
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Wow, I'm lookin' over yar sholders reading this thread. I gotta say, I learned more here right now on stuff I really need to know about brakes, and I really wasn't looking for it yet. All makes sense. Thanks folks. I'm watching. Time....



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