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Discussion Starter #1 (Edited)
2013 PSD KR
2006 Fleetwood Gearbox toy hauler 5er 2 axle 4 electric drums.


Latched to my trailer and pulled it out of hibernation a couple days ago. Manual override on the controller & only one brake would lock up. Upon further inspection I found a bad magnet (I think). Replaced all 4 brake assemblies with new just for piece of mind. Soldered in the new assemblies.

Now the brakes on the trailer will hardly hold me at slightly above idle using the manual override on the factory controller. No better using pedal. (gain set to 10) Yes my brakes are adjusted correctly, just a very slight drag with zero volts.

Tests I have performed:
12v+ at the 7 pin connector at the truck, engine not running. (dont know the amps)
7-8V at the magnets on all wheels, engine running. (tested at the wheels)
Pulled the breakaway switch and braking is not any better. Will not lock up. Not even close.

Assumptions I am making:
I have resistance somewhere in the trailer brake wiring.
By pulling the plug on the break-away switch, my truck is not the issue.

I have to assume that I have resistance somewhere in the trailer wiring to cause a voltage drop from 13+V when running to 7.5V+- at the magnets.

IF I am having resistance in the trailer wiring, resistance will go up with amperage. This may explain that with only one brake locking up and at least a bad magnet, I was not seeing full amp draw, hence lower resistance and more volts to the good wheel that was locking up.

Tests?
Clip the wire leading to the 2nd axle. This drops out 1 axle from the system. If braking is better (less amp draw, less resistance, more voltage) then my wiring throughout is suspect. (or there is an issue with the 2nd axle wiring)

With the 2nd axle disconnected, pull the break-away and see what happens.

Throw 12V into the 2nd axle from a battery (after after disabling it from the system) and the darn brakes should lock up. (I can also measure voltage & amps with a multi meter in series)

Hook up the rear axles using another male plug (and wire) and plug it into my truck, bypassing the factory trailer wiring and the first axle. See what happens.

Am I missing anything? What am I over looking? Am I full of crap?

I am leaving Thursday for Florida, fully functioning brakes or not. Obviously I would prefer to have 100% functioning brakes. That is why I am working in an unheated garage at 30 degrees! I need brakes! LOL

Any and all comments will be appreciated and digested to the best of my ability.
 

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The only suggestion I can make is to check the ground side. Good solid ground on the truck and the trailer is essential. As you correctly noted, higher amperage makes any resistance in the ground even more important.
 

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Did you adjust the brake shoes? There is a star adjustment just like on car drum brakes.
When you pull the emergency brake will the brakes lock up all the wheels?
 

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Discussion Starter #4
The only suggestion I can make is to check the ground side. Good solid ground on the truck and the trailer is essential. As you correctly noted, higher amperage makes any resistance in the ground even more important.

Agreed.


Although I have not found where the ground for the brakes comes from, chassis or truck. My guess is that the ground is direct from the truck. No evidence as of yet of a chassis ground.


It is 30 degrees out and snowing. My plan is to leave a day earlier, pull it to warmer weather, test and if I have to replace the brake wiring on the road.



Should be an interesting trip.
 

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Discussion Starter #5
Did you adjust the brake shoes? There is a star adjustment just like on car drum brakes.
When you pull the emergency brake will the brakes lock up all the wheels?

Yes I did adjust the shoes. Although I might have not adjusted enough. I adjusted so there is a very slight drag when jacked up & rotated. I did read a post saying they should be adjusted so the wheel makes one revolution when turned hard by hand. If this is correct I need to re-adjust.



Correct me if I am wrong here. The above adjustment will make no difference in why my brake magnets are only seeing 8 volts.



When you pull the emergency brake will the brakes lock up all the wheels?

Unsure what this exactly means.IF you mean the trucks emergency brake, I think that would be irrelevant. If you mean the breakaway switch on the RV, as stated in my original post, braking is unchanged (no lock up).



Thanks for the replies guys!
 

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The first thing to check with any electrical problem is the grounds. Especially if the trailer has been just sitting. Bad grounds do all kinds of weird things.

Your trailer should get the ground from a couple places from the truck. One is the ball or hitch but with your trailer being a 5th wheel the coupler will isolate it. The other is through the light plug. I would check where the ground from the light plug is connected along with what is grounding the axles.
 

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Had somewhat the same this fall with my trailer brakes. Ended up cleaning all pins in both the trailer pigtail and the truck coupler. Voila! trailer brakes again. Even better, I now run with a max of 7 on the controller
 

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The emergency brake controller gets it's power from the rv battery not the truck. If you only get 8 volts at the drums than you have a connection problem. Check the connection on the truck. Open the junction box on the rv and make sure all the wires in there are clean and tight.
 

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The voltage at the magnet will vary according to your brake controller setting and how hard you press on the brake (if you have the Ford built in controller). Voltage will vary anywhere from 5 to 12 volts. Amperage will increase also accordingly.
Your brake shoes aren't set tight enough. Pull the pin on the breakaway and a full voltage of the battery will be going to the brakes. Adjust until the tires stop within a rotation or so. The magnets are on an arm that swivels once they receive current and stick to the inside of the drum and pushes the shoes against the drum. The higher the voltage the less the magnets will slip thus pushing the shoes harder against the drum until it stops the wheel (when not under a load, it is possible that with a large load the brakes wold not lock up).
Just keep pulling the pin and trying to spin the wheel then put the pin back in and tighten the star adjustment wheel in between the shoes until you get the desired result.
 

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Yep, the wiring through the axle tubes are a huge issue! It ended up being my whole problem one time while on a trip and I had no brakes.
Ended up cutting one supply wire at a time and found that the right rear wire was shorted in the axle tube somewhere.
When wiring with new wire, I used the old wire to pull the much better new wire through the tube.
This is a link to the only wire I use now:
The answer to this and for safety also pick up a 4 wire fuse box and install a separate lead to each brake panel and if you have one brake short the fuse will blow but you will still have 3 working brakes.
Link to fuse box.
 

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