Wiring Brakes & Breakaway Switch - Fiberglass RV


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Old 06-26-2006, 08:53 PM   #1
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As I said in an earlier post, I am electically challenged, but when I looked at the brake wiring system, even I know it can't work! Have a look at this sketch:

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The blue lead from the umbilical is connected to the battery positive!!!, as is one each of the brake leads. The other brake leads are connected to the trailer frame, the trailer battery negative ground. Both leads on the Bargman breakaway switch are connected to the battery positive terminal!!!


Reading about brake wiring, I understand that the blue lead in the umbilcal cord must go to each brake,as well as the white negative lead. I understand that it is not a good idea to rely on the trailer ground to complete the connection, since those wires can and do break with the axle movement on the springs (as one of mine did). The sketch below shows brake only wiring as I understand it.

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I have not been able to find a good sketch of how to include the breakaway switch in the wiring scheme. This is my best guess. Is it correct?

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I will be checking with a trailer brake shop to be sure, but I want your opinions. As well:

Have the brakes been damaged connected as shown in the first sketch? As I read it, that wiring setup should leave them permanently on!

Has the breakaway switch been damaged with both leads connected to the positive terminal?
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Old 06-26-2006, 09:03 PM   #2
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I don't think the breakaway would be damaged, but I'm preety sure the brakes will be shot, if not the magnets may be.
the last diagram will work.
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Old 06-26-2006, 10:41 PM   #3
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[quote]I have not been able to find a good sketch of how to include the breakaway switch in the wiring scheme. This is my best guess. Is it correct?

Attachment 3671

It is correct.

I don't think the bargeman breakaway switch itself is damaged. As long as the pin remained in the switch, It remained in the contact open condition.

I cannot speak for the brakes themselves.
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Old 06-26-2006, 10:44 PM   #4
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Thanks guys, it really helps to have good input and direction so quickly.

Victor
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Old 06-27-2006, 01:41 PM   #5
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Victor, your logic and resulting wiring configuration look correct to me - you will end up with a set of connections which are functionally identical to what my Boler had originally, and what it has again after re-wiring (but now I have much better connections). The brake magnets are in parallel, with power from the blue wire and returning on another wire; the breakaway switch connects full battery voltage across the brakes, with the battery positive to the brake blue wire - both of these are correct as I understand the published guides and intended brake system operation.

In the original wiring, the brake magnets were <strike>shorted, and </strike> connected to power all the time. <strike> without a ground or return wire. In this configuration, I don't see how any current could flow, so I can't think of any way in which they would be harmed. </strike> For a check of my magnets, I measured the resistance between the leads with a meter: each should have a resistance of roughly 4 ohms, or about 2 ohms in parallel. Very much different might indicate an open or short circuit in a magnet coil or wiring.

<strike>Similarly, </strike> even if the breakaway switch were tripped, it would only connect wires in a loop without a voltage difference to drive any current flow; <strike>again</strike>, I don't see how anything could be hurt. To check, would again measure resistance with the switch wires not connected to anything else: it should be infinite (open circuit) with the plug still in the switch and near zero with the plug pulled. My original switch plug would not pull out, so I replaced it - I'm glad I checked.

My only caution would be to make the brake connections as direct as possible, so current goes through as few junctions as is reasonable, for reliability.
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Old 06-27-2006, 01:45 PM   #6
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Correction
Sorry - in my last post I forgot about the original ground connection to the brake magnets. If this was really a working connection to the battery negative, the brakes would be full on at all times, and thus by now would be worn out - and any connected battery would quickly go flat. Time to pull off the drums and have a look at the magnets...

This doesn't change the situation with the breakaway switch, or the validity of the proposed wiring (which I agree should not use the frame).
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Old 07-30-2006, 01:26 PM   #7
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Hi...I'm electrically challenged as well.

I had the torsion axle replaced on my trailer a couple of weeks ago. In exchange for some accidental damage to the paint and belly band, the shop installed electric brakes with a breakaway switch free of charge.

For some reason, they mounted an small battery to the frame which I assumed was only used by the breakaway switch. It looks like this small battery is hooked up to my main battery's positive / negative so I also assumed that the small battery is rechargeable.

While my kids were playing around in the trailer, they turned on a DC light even though my main battery was not connected. It now seems like this small battery is hooked in serial with my main battery. At the very least, it's not isolated to the breakaway switch.

Is this a problem?

Thanks...Kent
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Old 07-30-2006, 01:56 PM   #8
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Quote:
Hi...I'm electrically challenged as well.

For some reason, they mounted an small battery to the frame which I assumed was only used by the breakaway switch. It looks like this small battery is hooked up to my main battery's positive / negative so I also assumed that the small battery is rechargeable.

While my kids were playing around in the trailer, they turned on a DC light [b]even though my main battery was not connected. It now seems like this small battery is hooked in serial with my main battery. At the very least, it's not isolated to the breakaway switch.

[b]Is this a problem?

Thanks...Kent
From My understanding of the way things work, what you described meant that the small battery was hooked up in parallel with the main house battery. That would be how the circuit would be completed to run the DC lamp that the kids left on. If it were hooked in serial, the not connected main battery would have left the circuit open, preventing the DC lamp from lighting.

(1) Having a separate battery for the Break-away switch would be a "fail-safe" protection to make the brakes work if the house battery were disconnected.

(2) Connecting the Break-Away battery in parallel with the House battery would allow for recharging of the Break-Away battery from the trailer's established recharge line.

However, your kids have taught you that this system is NOT completely "fail-safe."

You can have (1) without (2) to have a "fail-safe" break-away system, but without a charge line.

(2) recharges the separate battery, but makes it totally redundant (and pointless) in the first place.
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Old 07-30-2006, 03:38 PM   #9
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They likely should have saved themselves some trouble and not installed the battery in the first place, because with a house battery, the brake battery isn't needed. Its function is to supply power to the brakes in the event of a breakaway (tow vehicle elec system no longer connected to trailer) for trailers that don't normally have a house battery, like boat, utility, motorcycle, horse, etc. trailers.

Perhaps the whole thing came as a kit and they didn't know how to install it without its dedicated battery
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Old 07-30-2006, 08:53 PM   #10
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An extra little battery simply connected in parallel does seem pointless to me.

Adding a diode-based isolator or charge controller between the positive terminals of the two batteries would provide the recharging ability and still supply breakaway braking in case the house battery were accidentally run down. For this to work, all house loads would be connected on the house battery side, and only the breakaway switch would be connected on the extra battery side.

I have seen specs for some breakaway systems which include battery charge controllers, so it has occurred to these suppliers that the battery could be run down by external loads (like the lights turned on by Kent's kids), rendering it useless when it is needed. Too bad the shop staff didn't think of this, but it could be added.
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