Forum Discussion

Homey_B's avatar
Homey_B
Explorer
May 01, 2015

Battery Switch and Brake breakaway protection

I've finally decided to install a battery cut-out switch in my Copper Canyon. It seems simple enough - put the switch between the battery and the junction block where the Positive lead is attached to the rest of the electrical system.

My concern comes from the emergency brake cutoff. I have read that you never want to cut the power from that system. It prevents you from driving off with the battery disconnected, leaving you with absolutely no emergency brake capability. Yes, I realize that if the breakaway switch trips, I have much bigger issues, especially with a 5th wheel!

So, let's just play this through. I have to figure out where the brake power comes from. There are four wires on the battery splice block. One is the battery. I presume another comes from the RV power distribution panel. The other two come from where I cannot say.

Or, let's work backwards from the breakaway switch. The two leads go into the RV through the same wire bundle that the tow cable follows. But once it gets into the base of the pinbox, it gets lost.

Are there any suggestions on how to locate this system so that I can wire it directly to the battery (and avoid the soon-to-be-installed disconnect switch)?

Any help you can offer would be greatly appreciated! Thanks in advance!
  • laknox's avatar
    laknox
    Nomad
    May 01, 2015
    My factory disconnect leaves the jacks hot, but shuts down everything else, including the charger. I learned that the hard way by showing up at a dry camp without fully-charged batteries, even though I'd driven for several hours. THAT was enough to be damn-sure the disconnect is HOT whenever I hook up.

    Lyle
  • Mile_High's avatar
    Mile_High
    Explorer
    May 01, 2015
    rhagfo wrote:
    Well it becomes a pre-tow checklist item!
    Battery disconnect switch to the ON position.

    Didn't give it a second thought when we installed our disconnect switch, we run with the refer on, so you need the switch to the on position for the frig to work! :)


    X2

    I'm rewiring my cutoff to be a true cutoff, and I'll cut the breakaway as well. To be honest, I accidently pulled the breakaway while putting it in storage, and it killed my batteries and I had to replace them. Had my cutoff been a real cutoff, I wouldn't have had to worry about it.

    Just hang a tag on your breakaway cable to remind you to turn on the switch if you are getting as forgetful as me.
  • okan-star's avatar
    okan-star
    Explorer
    May 01, 2015
    The blue brake controller wire runs from the truck to the brakes direct
    The breakaway switch has two wires , both usually black , one will go to the fifth wheel side of the black charge wire in the 7 wire harness from truck to 5th , the other will go to the blue controller wire
    When the breakaway is pulled it sends 12 vdc from the black charge wire to the blue elec brake wire , engaging the brakes fully , this needs to happen obviously when the 5th is not connected to the truck
    Find the black charge wire at or near the battery
    The battery disconnect has two connections on the back , one hot and one swiched- disconnected when turned off
    Put the black charge wire on the hot post along with the cable from the bat , that way the breakaway will have power when the bat switch is off , also you will then get charge from the truck when the switch is off
  • TucsonJim's avatar
    TucsonJim
    Explorer II
    May 01, 2015
    clotus wrote:
    I am assuming your landing gear power is cut with the switch as well. If this is the case, as is mine, I have to turn the battery on to hook it up, so I am not worried about forgetting that step.


    ^^^ X2 ^^^ If you have to turn on the switch to operate your landing gear, you won't have an issue.

    And as others have mentioned, you should have a checklist you follow when you hook up. Make sure that is the first step.
  • B_O__Plenty's avatar
    B_O__Plenty
    Explorer II
    May 01, 2015
    Mine is set up to shut everything off. When towing it has to on to allow the jacks to operate. It also has to be on to allow the battery to charge from my tow vehicle. I can see no reason to turn it off except when in storage..

    B.O.
  • clotus's avatar
    clotus
    Explorer
    May 01, 2015
    I am assuming your landing gear power is cut with the switch as well. If this is the case, as is mine, I have to turn the battery on to hook it up, so I am not worried about forgetting that step.
  • RustyJC's avatar
    RustyJC
    Explorer
    May 01, 2015
    The ohmmeter is your friend. Lift all 4 wires from the battery+ terminal of the distribution block. Be sure the RV is unplugged from shore power so that you don't have the converter trying to charge the battery (probably one of the wires going to that terminal). Now, measure each wire's resistance to chassis ground and, while doing so, pull the breakaway switch. When you find the wire whose resistance drops from infinity to a very low level, you've found the wire going to the breakaway switch. Wire it upstream of your battery disconnect switch so that it always has power.

    If all 4 wires are tied to the positive terminal of the distribution block, I'd bet they are the following:

    1. 12VDC power from the umbilical cord to allow the truck's alternator to charge the battery while traveling.

    2. 12VDC power from the converter to charge the battery while plugged into shore power.

    3. 12VDC to the 12VDC power distribution (fuse) panel in the RV and then on to the 12VDC loads.

    4. 12VDC power to the breakaway switch.

    Rusty
  • Old-Biscuit's avatar
    Old-Biscuit
    Explorer III
    May 01, 2015
    Do you have just 2 wires on the 'switch'?.....should be BLUE.
    One goes to battery + and other ties into line going to brakes from umbilical cord (blue)

    3 wires on 'switch',,,,,,,,,white is ground (frame), black is battery + and blue (umbilical cord)

    Probably need to access umbilical cord connections........my overhang has access panel next to pin box........and check how 'switch' is wired
  • rhagfo's avatar
    rhagfo
    Explorer III
    May 01, 2015
    Well it becomes a pre-tow checklist item!
    Battery disconnect switch to the ON position.

    Didn't give it a second thought when we installed our disconnect switch, we run with the refer on, so you need the switch to the on position for the frig to work! :)

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