Breakaway Switch Melted/Burnt

[ttsr4us]

Airstream 2015 Flying Cloud 27FB

Well, Friday night our house washing machine broke down and today wanted to tow the trailer to our house to load up /clean tank/ for our trip starting next friday. Was hitching up and connected/pulled the cord on the breakaway switch and noticed the plastic covering was melting and burning.

Turned off the 12 volt but too late. Anyway, I pried the contacts apart stopped the process. Would like to know if a brake/12 volt electric/or just bad switch caused this issue.

Any ideas on how to proceed? I'm talking to Airstream tomorrow.

:M:E

[Turtle_n_Peeps]

jerdew wrote:
In reading this forum entry, I now have a question that is puzzling me. Since the trailer brakes do not engage unless the trailer is moving (i.e. the wheels/drums are rotating), how does the manual override on my brake controller set the trailer brakes when I am hitching/unhitching and the trailer is stationary?

The magnet will stick to the drum face anytime juice is applied. When this happens and "if" the drum rotates (even a few inches or less) the shoes will deploy and lock up the brakes.

[jerdew]

In reading this forum entry, I now have a question that is puzzling me. Since the trailer brakes do not engage unless the trailer is moving (i.e. the wheels/drums are rotating), how does the manual override on my brake controller set the trailer brakes when I am hitching/unhitching and the trailer is stationary?

[jerdew]

Just to add a little more to this topic ...
I was backing my 5th wheel into a tight spot and making some sharp
turns, and either my breakaway switch plug fell out or the wire got
caught on the hitch, which pulled the plug. Either way, we soon
noticed smoke coming from behind the trailer tires. I crawled under
and saw that the insulation on the wires running to the brake on the
front trailer tire was melted and the wires were shorting together.
I crawled out from underneath the trailer, hurried to the TV and
quickly disconnected the trailer cable. At that point, I noticed
that the breakaway switch wires were also smoking/melting and the
switch was melting. I then ran to the trailer, fumbled for my keys,
and unlocked the battery door and disconnect the trailer battery.
That stopped the immediate problem, but now I had others. I had to
be towed to a repair shop that could fix and inspect the brake wires
(including the wires to the magnets inside the hubs), and replace the
breakaway switch. My month-old RV batteries also now seem to be shot
since they will not keep a charge and the electrolyte measures
nothing on a hydrometer. All of this is just to point out that
a pulled pin on a breakaway switch can cause a lot of serious
problems.

[BurbMan]

BarneyS wrote:
If the wheel is not moving, there is no movement of the brake pads, therefor no braking occurs. It cannot happen if the trailer is standing still.

Correct, the breakaway switch is not a parking brake. The magnet grips the face of the drum, and the rotation of the wheel forces the shoes against the sides of the drum.

In order for the breakaway switch to hold the trailer in place it would need to roll a little first.....

[Old-Biscuit]

WHY do you have to pull pin to wrap cable around bumper?
Cable should have loop on end......get a carabiner or 'S' hook with spring clip and attach cable to safety chains.
Emergency Break Away Switch shouldn't activate unless trailer is completely disconnected from tow vehicle........ trailer jumped ball, safety chains broke, umbilical cord pulled out...trailer run-away


When you pull pin.......full battery voltage is going to trailer brake magnets
and IF truck/trailer umbilical cord is plugged in.......you can backfeed to brake controller in truck.

Applying full battery voltage to magnets.......not an issue unless it is done for extended time (hours) and then damage could be done to magnets/wiring etc.

Depending on which brand of brake controller......could burn it out

[Hornnumb2]

So when I am hooking up my trailer I pull the pin to loop it around the bumper, am I messing something up doing this?

[Old-Biscuit]

Energize the magnets....they try to stick to face of drum
When drum rotates.......magnet movement causing the actuating arm to pivot, spreading the brake shoes, causing them to come in contact with the brake drum and apply the brakes.

Energized magnet.......no drum rotation.......no brake shoe movement JUST an energized magnet which gets hot

[BarneyS]

bucky wrote:
OB I respect your opinion almost always so please explain how the brake shoes know that the trailer is moving.

Hi Bucky,
The magnets are mounted on the brake pad plate, once the magnets are energized, the brake pads depend on the rotation of the wheel to move the brake pads out to contact the drum. If the wheel is not moving, there is no movement of the brake pads, therefor no braking occurs. It cannot happen if the trailer is standing still.
Take a look at the pictures in this post and you will see why. There used to be an animated diagram showing how the brakes work but I cannot find it right now. If I do, will post in in this thread.
Barney

[bucky]

OB I respect your opinion almost always so please explain how the brake shoes know that the trailer is moving.

[ttsr4us]

Thanks for the info. New Switch on order. I'm taking it to the dealer for a recall before we set off for our long trip. Will get them to check the brakes.

Brian

[Old-Biscuit]

Yep..3A draw per brake magnet.........minus resistance thru connectors/corrosion
Per Federal Law...suppose to provide full battery voltage for 15 mins

Get new switch....check wire/connections/insulation for any damage


And anyone that pulls pin out to use as a parking brake doesn't understand trailer electric brakes.
Magnets will get energized due to full battery voltage BUT brake shoes do not engage unless trailer is moving. Sitting parked .magnet just gets HOT and battery has unnecessary draw

[RoyB]

The only way these contacts get closed in when you pull the KEY out.

Like said above they are NOT designed to be left in this mode very long.

Each BRAKE MAGNET will draw 3 AMPS when 12VDC is applied...

If you have two axles then that is around 12AMPS of DC CURRENT for four wheel electric brakes.

ETRAILER.COM should a good replacement switch assembly for you...

I have heard on here of some users like to pull the KEY to use as a brake to hold the trailer in place. This really isn't a good idea as you can see what happens to the contacts and the BRAKE MAGNETS can also melt down which is probably on the expensive side.

Something like this google photo



Roy Ken

[Turtle_n_Peeps]

Brake magnets draw a lot of amps. The brake away switch is designed to close and lock the brakes up in the event of a brake away.

They are not designed to be closed for a long period of time because of the amp draw.

It sounds to me like the switch was closed for a long period of time and went past it's duty cycle.