Brakes without battery

[[email protected]]

I have a 2009 2619 and turn my battery off. Will my break away switch operate this way?

[tentcamper]

The breakaway brake most likely will not work. This is the cable that attaches to the hitch and is engaged if the trailer breaks away from the hitch, it applies the brakes so its not running all over the highway.

On both my TM's the breakaway brake switch came from back by the converter. I had to re-wire the switch directly from the battery. Your normal electric brakes will work because they are power from the TV via the brake controler you had installed.

Y

[Bill]

To restate, if you turn off the TM battery, using a switch or any other method, then the breakaway brakes will not work. Remember, the breakaway switch is activated when the pin is pulled out of it, and this happens only when the trailer "breaks away" from the tow vehicle. When the trailer breaks away, and runs off on its own, the big cord from the 7-pin connector on the tow vehicle to the TM will be torn out, so the tow vehicle can no longer power the trailer brakes. The TM battery will power the brakes ... unless you have disconnected it.

Bill

[Padgett]

BTW was pulling a big race car on an Interstate when the hitch broke. The chains held and was able to bring the rig to a stop without incident. With a proper system and separate chain mounts, breakaway would require a quadruple failure- hitch, two chains, and the nut behind the wheel. First rule in racing: never do anything sudden..

[dab1950]

I have a 2009 2619 and turn my battery off. Will my break away switch operate this way?

When you say you 'turn my battery off', do you mean, you have a battery
disconnect switch or do you pull the 30 amp fuse or just simply disconnect
the red wires at the battery post?
Note; I said 'wires' as there are 3 red wires on my battery positive post.
The big one has the inline fuse and goes to the converter. The two smaller
wires goes to the electric brakes, one per.
If you keep the smaller red wires connected to the battery even though you
interrupt the connection to the converter, your break away switch and system
will remain at the ready if needed. However, if you disconnect all 3 wires,
then the TM is vulnerable to major damage. Albeit very remote as Padgett
explains; quadruple failure.
So, my advice, don't disconnect the smaller red wires to the battery positive
post. They have no current through them unless the switch is activated so
there won't be any drain on the battery.
Hope this helps.

[Bill]

I said 'wires' as there are 3 red wires on my battery positive post.
The big one has the inline fuse and goes to the converter. The two smaller
wires goes to the electric brakes, one per.I'm not sure I understand this. If you have two wires directly from the battery post to the brakes, then the brakes will instantly slam on as soon as you make the connection. That can't be right.

If you meant that the two smaller red wires go to the breakaway switch, then there is no need for two wires. Only one wire goes to the breakway switch, and only one wire comes out of the breakaway switch. This wire goes to the brakes as a pair, first to the left brake, and art the brake, the second wire to the right brake is connected.

So while I agree with you that the large red wire with the 30 amp fuse goes to the converter, I have no idea what the two smaller red wires are for. Do you have an electric tongue jack? That could be one of them. You mention that you have electric stab jacks. Can you activate these as pairs (front pair and rear pair, or left pair and right pair)? Do you have solar panels?

I guess my bottom line is that very few TMs have 3 wires at the positive post of the battery. Your extras are most likely part of some aftermarket items.

Bill

[commodor47]

Bill,

Like you, I don't see how the two extra red wires could be used to power the brake away switch.

His signature indicates he has electric stab jacks. My guess is the front and back pair of jacks are wired separately to the battery. That could be the two extra red wires he is referring to in his post?

Hopefully he will reply with confirmation as to my guess.

Dick

[dab1950]

Bill and Dick,

I have no electric tongue jack and no solar panels. Maybe you are right about
the extra two red wires providing power to my electric stabilizer jacks. I need
to check on that.
But it's my understanding, the 2006 2720 with the battery mounted in the
rear storage compartment, the extra red wires are connected to the brake
actuators and the break away switch on the tongue applies frame ground when
the lanyard is pulled thus completing the circuit and applying the brakes.
However, I have a PDF of the 2008 TM Owners manual. Does the 2008 2720
have the battery in the front? On page 38 of my PDF is the discussion and
schematic of the break away switch circuit. This schematic is exactly opposite
to how my 2006 is wired(I think)(need to double check this). This PDF shows
the 12V + 'hot line' is common with the blue wire line in the Bargman connector
which is connected to the brake controller in the TV.
Where is the battery on the 2009 2619? If it is mounted on the tongue, then
the advice I gave above is very likely wrong and misleading. if that is the case,
please accept my apologies.

[Bill]

I think you are now headed down the right path. There is a +12 volt wire from the hot side of the converter (probably not directly from the battery) to the breakaway switch. Then, a single wire from the breakaway switch is spliced into the blue wire from the brake controller to the brakes. This splice is part of the mass of wiring behind the refrigerator (lower panel, removed from outside).

It is almost unheard of for a switch to actuate a circuit by applying ground, and for good reason. It is actually illegal for this to be done on 120 VAC power distribution.

I updated my TM Wiring Diagram and attached it here. It is electrically correct, but physically a bit abbreviated because it does not show all the 12-volt fuses. But it does show how the brakes are powered, where the power gets to the breakaway switch, and how it gets from the breakaway switch to the brakes. It also shows how the battery is tied into the whole system.

My guess is still that the red wires go to your stabilizer jacks. Easy to check. Just remove the wires and see if the jacks still work.

Bill

[dab1950]

Bill,

I'll check on my wiring. But just to be sure, [email protected] isn't confused,
if you disconnect the battery from the rest of the TM, then the break away
switch is isolated too. Not good.
Thanks for all you do Bill.

[[email protected]]

Yes my battery is on the tongue and I have a switch to totally isolate the battery
I will now turn it on while towing
Thanks to all

[Shane826]

Bill-
Just a heads up; it’s very common for cars and trucks to apply ground to complete a circuit.

[Bill]

I stand corrected. I realize that a lot of low-voltage low-current electronic signals are done this way, but here we are talking about a power circuit big enough to require a fuse for safety. Can you give me a couple examples, so I won't make the same mistake again?

Thanks

Bill

[Shane826]

Pretty much anything that’s module driven, the module switches ground. Power windows also come to mind off the top of my head.

But I agree in 110V world it doesn’t work that way. U

[klpauba]

I'm a bit confused (a common situation for me).

If the emergency brake is switching negative, wouldn't the other side of the brakes (the positive coil side) always be at a positive potential?

[BrucePerens]

I'm a bit confused (a common situation for me).

If the emergency brake is switching negative, wouldn't the other side of the brakes (the positive coil side) always be at a positive potential?

It's related to a very important electric principle, which can be stated this way:

What is the sound of one hand clapping?

You need a circuit for current to flow. This is a complete path from one of the poles of the power source, through the load via its two poles, and back to the other pole of the power source.

If any part of the circuit is missing, whether it is on the negative or positive side, no current flows.

"Ground" is a concept for a common or safety bus or plane which is part of the circuit.

[Larryjb]

In low voltage DC circuits you can get away with placing the switch on the ground side of the load (lamp, brake, window motor, etc). AC circuits have the switch before the load so you can't accidently electrocute yourself. Imagine changing a lightbulb and accidently touching 120 V in the socket. Or is possible, but tougher to do.

[klpauba]

More to the point, if the neg is switched and the other side of the coils are always at the pos potential, the brakes will activate only if the lanyard is pulled and completes the circuit.

So if the coils are always at the pos potential, what good is the TV's brake voltage? There's no complete circuit since the safety switch is open (and therefore no grounding). Wouldn't this mean there are no brakes while towing?

[Bill]

If the emergency brake is switching negative, wouldn't the other side of the brakes (the positive coil side) always be at a positive potential?We seem to be circling around the concept, but not quite homing in. Yes, klpauba, if the switch is on the negative side of the brakes (it is not), then the other side of the brake would always be at positive potential. Electrically there is nothing wrong with that since, as Bruce points out, no current would flow so the brake would not be energized. And if you close the switch, then current would flow and the brakes would be energized. This is just what is intended.

But with the switch on the negative side, a problem arises if any wire anywhere on the negative side of the brakes touches ground for any reason. Maybe the insulation got frayed, for example, and touched the trailer frame. When that happens, current flows through the brakes and the brakes slam on. If you are driving down the road, and the brakes slam on without warning, it is a safety issue. As Larry points out, this is NOT what you intended, and there is no protection. By contrast, I suppose that if your dome light comes on unexpectedly, it is not a safety issue, so the dome light switch could be on the negative side (I don't know that it is).

So a frayed wire on the negative side could be a problem. But to be fair, it is also possible that a wire on the positive side of the brakes or dome light could fray and touch ground. What happens then? Simple. A fuse blows, but no other harm is done. It is annoying, but it is not a safety issue.

Hope this helps. If it is still confusing, I can put together a quick sketch to illustrate.

Bill

[klpauba]

Thanks Bill.

Your (and others) complete description aligns with my understanding -- no matter where the switch is in the circuit (positive or negative "side"), it will function the same. Maybe a diagram will help but please include the positive wiring from the Bargman connector in conjunction with the negative side safety switch. Earlier, a TM owner mentioned that his safety switch is on the negative side -- unlike my positive side (as are most/all TMs). I can't picture how the TV positive (and variable voltage) would work in combination with a negative side safety switch.

Feel free to PM me if you think it doesn't add to the discussion.

Thanks!

[Bill]

Earlier, a TM owner mentioned that his safety switch is on the negative side -- unlike my positive side (as are most/all TMs). I can't picture how the TV positive (and variable voltage) would work in combination with a negative side safety switch.I can't imagine how it would work, either. I think the statement was incorrect.

Bill

[Shane826]

No other harm other than your fuse blows and you have no trailer brakes...

[klpauba]

I can't imagine how it would work, either. I think the statement was incorrect.

Bill

Thanks, all!

[Bill]

No other harm other than your fuse blows and you have no trailer brakes...I look at it this way. If you get a short with a negative-side switch, the brakes will slam on unexpectedly. Depending on the circumstances of the moment, this may cause an accident as you, or other drivers, attempt to react. This is especially true if the pavement is slippery. It may cause your wheels to lock up (not so much on a TM, but on other RVs). Regardless of whether the wheels lock, if you are in one of those construction zones where there is no breakdown lane, or if you are on a city street, you may have to drag your trailer, against the fully-energized brakes, for some distance as you look for a place to pull off. Once pulled off, you have to make repairs on the spot. It may cause damage to brake parts. And you know it will happen in the least convenient place and time.

If you get a short with a positive-side switch, the fuse blows, and the display on your brake controller goes dark. But nothing dramatic happens, and if you are paying attention, you can opt to slow down to a safe speed, and drive to a safer or more convenient place, without causing damage or danger. In other words, you can handle it safely.

The choice isn't hard, and that's why most switches and fuses are put in the hot side of the controlled device.

Bill

[tentcamper]

Positive switch, with the camper disconnected where will it get the power from? From the switch one end go to the +12V the other end go to the brakes. The battery is the only place to get power when the trailer is rolling down the road.

Fuse?? there seems to be two schools of thoughts on fusing the breakaway switch. 1) protect the circuit for shorts. 2) don't protect the circuit, if the circuit is activated in an energy. Give it all to stop. This school does not want a missing fuse, bad fuse, bad connections in the fuse housing, or insulation missing on the wire to short to make the brakes inoperable.

I have had 6 trailers from 5 the different manufactures and its near a 60/40 which school they are from. I use to be on the side of fusing and added fuses, but now i'm on the side of no fuse and remove them. I want it to give it's all, including burning off the insulation of the wire, if need be.

[Bill]

Fuse or no fuse? I've wondered about this myself. In my Blue Book, there is a wiring diagram from Bargman, showing how the 7-wire connector should be wired. Beside it, there is a diagram showing the wiring of the breakaway switch. It shows no fuse. In this diagram, the 12 VDC hot wire from the TM battery goes directly to the breakaway switch. The other side of the switch is spliced directly into the blue wire from the brake controller, the wire that goes directly to the brakes.

So at least Bargman agrees with you, tentcamper. I do, too.

The wiring diagram from the TM Owner's Manual (from the factory) disagrees. It shows that the 12 VDC hot wire from the tow vehicle goes to the breakaway switch and the brakes, with no fuse. It also shows that this tow vehicle hot wire goes through the TM's 30-amp main fuse, and only then goes to the TM battery. This makes no sense to me , but I believe that the TM is wired this way.

Bill

[tentcamper]

I ended up disconnecting the positive side of the breakaway switch and wiring directly to the battery. We ended up with three wires on the plus side of the battery: 1) wire to converter, 2) wire to elec jack, 3) wire to breakaway switch. It was simple on my model to move the breakaway wire, because the battery is up front. When I removed the wire nut on the plus wire on the breakaway switch. The wire length was long enough to reroute to the camper battery.

My motive was to be able to turn off the + battery wire that runs back to the converter when traveling. This would allow us to run the 12v fridge, from the 12V battery wire from the TV and drain the camper battery. But I did get rid of the fuse.