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Break Away Switch

All photos are thumbnails, click on a picture to see a larger version

One area of pop up ownership that people commonly ask questions about is the break away switch. 

Federal traffic safety law specifies that all trailers that are required to have brakes, shall have a means of activating the trailer brakes under trailer break away conditions. 

Specifically, 49CFR393.43 states:  

Breakaway and emergency braking

(a) Every motor vehicle, if used to tow a trailer equipped with brakes, shall be equipped with means for providing that in case of breakaway of such trailer the service brakes on the towing vehicle will be sufficiently operative to stop the towing vehicle.

(b) & (c) deal with tractor trailers

(d) Every trailer required to be equipped with brakes shall be equipped with brakes of such character as to be applied automatically and promptly upon breakaway from the towing vehicle, and means shall be provided to maintain application of the brakes on the trailer in such case for at least 15 minutes.

If the trailer is required to have brakes, it is clear that the the emergency breakaway regulations require that the trailer be provided with an emergency battery backup system, that will provide electrical power to the brake magnets during the trailer break away brake activation process

So, the break away switch is a device that will engage the trailer brakes should it become disconnected from the tow vehicle.  Depending on state (jurisdiction) brakes are required on trailers of differing weights.  If you are required to have brakes, you are required to have an operational break away switch.  If in doubt, check with your local Department of Motor Vehicles.

The descriptions I use will be based on my Coleman Pop Up, but the theory is the same and should transfer to a pop up of any manufacture that has electric brakes.

In order to have a break away switch you need three things:

  • A battery on the pop up.  Once it becomes disconnected from the tow vehicle you will need a source of electrical current back there.
  • Electric brakes installed on the trailer.  The method I am describing here will not work with surge brakes, so if you have surge brakes you can stop reading now and stop by your dealer.  Surge brakes have different requirements for a breakaway system.
  • The switch itself. The switch will be a normally closed switch, which has a plunger inserted to open the switch.  When the plunger is pulled, the switch closes and current flows.  These switches are available at almost any RV parts dealer.

It is actually quite simple to hook one up. Take a look at the "A" frame of your pop up.  You should easily find the location where the wire bundle from the "back end" appears at the front end.  You will generally find something similar to what I have on mine, 3 "wires":

  • Two wires together that are the 12v DC positive and negative wires from the converter for charging the battery.  On mine they are black and white, terminated in a quick disconnect plug.
  • A large wire bundle that ends in the 7 Pin Bargman connector.
  • A single wire all alone (on my 2001 it is a blue wire) This single wire is the one you hook up to the switch.

So, once you locate the wire you think is the right one, time to test your theory.  Touch this wire to the positive terminal of the battery and you should hear the brakes engage.

To hook up the switch connect a wire to the positive terminal of the12vConn.jpg (52098 bytes) battery, or tap a new wire into one that is already there. Connect this new positive wire to one side of the switch. Connect the other side of the switch to the wire you identified that activates the brakes.  For this system to work there is no need for a negative wire as both the brakes and the battery use the frame as a ground.  In the picture to the right, you see the switch on the right side of the A frame.  If you look closely you will see one of the switch wires is connected to the battery positive wire and the other is connected to a blue wire (on my pop up that is the wire that goes to the brakes).

Leading off the plunger is a cable.  When hooking up your pop up for towing, this cable should be connected to some part of the tow vehicle.  Now, there are two differing opinions on the length this cable should be:

  • Longer than the safety chains so that the brakes will be applied after a complete separation of the tow vehicle and trailer
  • Shorter than the safety chains so that the brakes will be applied after the trailer separates from the ball, but before the chains break.

OK, so what happens with each option?

  • If the breakaway brakes are not applied until loss of chains, you will have a trailer that is surging, rebounding, and banging into the tow vehicle. The tongue will not gently or quietly follow the tow vehicle, and that electrical connection you are relying on to activate the trailer brakes may be ripped out inside the first two seconds. With all that motion, including forward/backward, up/down, and side/side, there is a significant risk of loosing the chains as well as the electrical connection, and then you have a loose trailer on the road.
  • If the breakaway brakes are applied while the trailer is still connected, there is a risk that the breakaway activation itself could cause the chains to fail, especially if there is more than an inch or two of slack left in the chains. (Who measures that to the inch?) Even if the chains don't fail, unless your brakes are too small for the trailer, the breakaway brakes will lock the trailer wheels. Locked wheels have no directional control, and so the trailer now will not reliably track the tow vehicle. It can easily end up far to the side of the tow vehicle, and in that position has a high possibility of rolling.

Which is correct?  I can find nothing in any statutes/laws that provide guidance.  You have to decide for yourself what you feel comfortable with.

I take the second option, brakes are applied before the chains separate.  But, now comes the hard part, with this option the cable should be shorter than the safety chains but sufficiently long that the cable will not activate the brakes when you turn.  It may take several tries to get the right length.

The theory is that should your pop up disconnect from the tow vehicle, the trailer will fall back from the tow vehicle.  If the chains are the correct length and are crossed in an "X", the chains will cradle the front of the A frame.  Now, if you measured the break away switch cable correctly, it will have been shorter than the chains and will have activated the brakes as the trailer fell back  With the brakes fully activated, the trailer should track fairly straight and allow you to pull to the side of the road.  Should it happen, you will probably need a new set of tires, as locking the brakes at full speed is not great for the tires, put you should still have a pop up.  Oh, you will probably need new undies too.

In case you wish to do a little more reading on this subject, the following documents address breakaway systems:


Classic Trailers Owners Manual

Trailer Canada, Trailer Safety Tips

BrakeBuddy Brakeaway Installation Manual


Lets hope you never need to use the break away switch.

Please note, do not pull the plunger to set the brakes.  Your battery will quickly go dead an you will no longer have anything holding the trailer (the brakes will release when the battery dies).  Always use chocks to keep the trailer from rolling!




   Revised: May 08, 2007


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