more about electric brakes

[openroad]

I feel like a babe in the woods. I'm now able to tie the dead battery, the onboard charger always loaded,even if I thought everything was turned off,to the break away switch. Is this why all my brake magnets had a wire burnt off?I think with the pin pulled,there is always a feed to the brakes. duh! Harness is wired correct.

[71_safari]

If you are saying that you were pulling the pin when parking the trailer - yes, it will create a constant draw, trying to hold the brakes on. I suppose it could eventually fry the wires. That pin is only for emergencies when the trailer gets loose, as you know. Interestingly, when I was last at the Airstream dealer in Eugene to have my brakes adjusted, the service advisor mentioned that a recent customer was also pulling the pin, and always had a dead battery in the morning. Apparently this is something that has not been explained to folks well enough.

[overlander63]

Even worse, if you do this, it is very possible to burn up the magnets in the brakes, also. One of these threads contains a post from Andy at Inland (Ithink) that states you shouldn't leave the pin pulled out on your breakaway switch for more than a couple of minutes at most, or you may fry the electric part of the magnets.

Terry

[john hd]

and detemper the spindles on your axles!!!

john

[CanoeStream]

A good thread: Breakaway switch

All learning curves are uphill, ain't they? Been there -- am still there. Welcome to ASForums and come back often! No question is 'too smart.'

[openroad]

after the feed comes onto the yellow wire from my brake controller,where does it go?I'm assuming it gets to the magnets in all the wheels to apply the brakes. I also think a fully charged battery in the trailer puts a feed to the magnets if the pin on the breakaway is pulled.what I can,t understand is how this circuit is wired. My electrical diagram in the airstream book does not dig this deep.Does anyone have this info? I would be grateful.

[87MH]

Originally Posted by openroad

......after the feed comes onto the yellow wire from my brake controller,where does it go?

I have just "opened up" the front interior of the '78 Sovereign, and this is what I have found....The yellow wire from the Brake Controller ties into a black wire, which is paired to a white wire from the "ground" bus in the fuse/battery box. These two wires run in a "red" sheath to the underbelly and then ultimately to the brake magnets at the wheels.

Now, where the "yellow" Brake Controller wire (+/- 6 volts) ties into the "black" wire, there is a third wire, "blue" in my case, that ties into the same crimp connection. This blue wire comes from the "break-away" switch at the hitch. The "blue" wire gets its power (voltage) (when it is closed or "activated") from the same wire (red) that supplies power to the electric tongue jack.

What this means is that when the "break-away" switch is activated, full (trailer) battery voltage (12 volts +) is sent to the brakes.....this is more or less a direct short connection via the brake magnets. This "short" will either deplete a battery or burn a wire (or magnet) in short order.

The (red) wire to the electric jack is protected by a 30 amp (I think) breaker, so there is plenty of basically unprotected "juice" flowing to the brake magnets when the break-away switch is closed. The breaker protecting the jack is visible when you remove the inner cover of the 12 volt fuse box. On the extreme right hand side (on the '78, anyway) will be two breakers, the upper breaker is connected to the feed (blue wire) from the charging circuit of the Tow Vehicle, and the lower (connected to the red wire) is the breaker protecting the Electric Jack/Break-Away circuit.

[Ed Keyes]

Have a Hensley Hitch and on occasiond found it is helpful to pull the pin when I am taking the hitch bar from the hitch box. Even when I jack the trailer to what I consider the ideal height, in some situations the truck wants to drag the trailer even though the wheels are blocked. I replace the pin as soon as hitch bar has cleared.

[Over59]

I'm not sure what problem you are trying to solve. A wire (mine is red on the 68) is attached to that breakaway switch. The switch is bolted to the frame. When the pin is in the circuit is held open. When pulled out the circuit is closed and the magnet energize. The magnet already has a 12v load on it. If the controller or the switch connects the mag to ground then the brakes go off. The load (juice) if from the common bus which connects the battery bank and tow veh charge line.


Now I belief this to be true but a confirmation from the forum EE would be welcomed.

[john hd]

i'll see if i can come up with a diagram and explanation later...

i just got home from work at the power company had to deal with a transformer full of RATS! and gnawed off wires!!

i have to go drink some beer and go wash the rat cooties off me!!

i'll get back, pm me if i ferget!

john

[openroad]

thanks for all the input to my wiring electric brakes questions. I think in my 69 vintage it used two wires ,to the breakaway switch. also a black and white to each wheel magnet are probably joined to the yellow(brake) wire,and also to the breakaway switch.

[john hd]

ok,

here are some diagrams that may help somewhat.

john

[john hd]

and the trailer

[greg176]

Just a note on what I have been reading about breakaway systems.Tekonsha sells a 4 amp hour battery and charger for the trailer power source.Perhaps if this was used instead of the trailer's deep cycle battery an accidental pulling of the pin would not result in burnt magnets,wiring and toasted spindles.

[CanoeStream]

An engaged brake is an engaged brake. These are not like emergency brakes in cars that can be left on. Authorities seem to say 5 minutes is too much, whatever the source.

Self-contained battery-breakaway systems are sold for trailers that otherwise wouldn't have a source of 'house power' if disengaged from the tow vehicle.