BreakAway Switch Help

[Siegmann]

Over the years I have tested my breakaway switch from time to time. It always worked. But I decided that the switch itself was looking a little too rusty, and the plastic pull-out part a little too brittle, so I decided to replace it. After installing a new one, I tested it, and it did not activate the brakes. The brakes had worked while towing, just a few days before when I had parked the rig. I have 12V power at the breakaway switch and also bypassed the switch by jumping the wire leads where they had 12V, but still could not activate the brakes. Any ideas?

[SteveH]

If the brakes work from the TV controller, and there's power into the switch, the only thing it can be is a bad switch, or a wiring problem.

Check the switch out of the circuit with an ohm meter, and it should read a short with the pin pulled.

If that is good, you should be able to read battery at the brake input terminal at the 7 pin connector when the pin is pulled with the switch in the circuit.

If the switch is good, but you don't get battery at the brake input terminal with the pin pulled, it's a wiring problem.

[Siegmann]

I do get 12v at the brake input at the 7 pin connector when I pull the pin on the breakaway switch. Any other ideas?

[Protagonist]

Check for a blown fuse. If you did not pull the fuse or disconnect the battery before doing the work, you may have accidentally short-circuited the wires when you snipped them to remove the old switch. The wiring to the switch is live even when the main disconnect is in the "store" position.

[SteveH]

Originally Posted by Siegmann

I do get 12v at the brake input at the 7 pin connector when I pull the pin on the breakaway switch. Any other ideas?

Your brakes should be working then. You might want to check the voltage at the brake magnets when you pull the pin, and if you don't have 12VDC there, the problem is in the wiring between the harness and the brake magnets.

[Siegmann]

I dug up my wiring diagram, and there is an aux 20 amp, type 2 breaker, between the blue 12 ga. wire from the breakaway switch and the batteries. It's got continuity. On to checking voltage at the brake magnets. But I can always hear a nice "hummmm" from the brakes when they are activated, and I'm not hearing that.

[Siegmann]

OK, I've got 12v at the brakes, but when I pull the pin on the breakaway switch, I just get a "click", but no "clank" and "hummmm" like I got when I just hooked up the tow vehicle and engage the brakes. I'm on an extremely un-level site, so I have not yet done a tow test, or raise up one wheel free, to do do a spin test.

But I'm curious, do others find that the brake engagement is less energetic/loud when testing the breakaway switch vs. when the brakes are engaged by the tow vehicle?

[SteveH]

The only indication I ever got when the trailer was not moving was the clicking of the magnets hitting the surface of the drums.

[Silver Goose]

In normal operation, the brake controller may send 2-4 volts to the brakes, maybe more if you operate it manually. The breakaway switch dumps a full 12 volts to the brakes when the pin is pulled so it should be more noticeable. I'm assuming your trailer battery is fully charged? Some have used a compass to determine if a magnet is energized, but I've never tried that myself.

[Siegmann]

I have hook-ups but unhooked for this test. The voltage measured at the breakaway switch was 12.6. A real puzzler as to why the response at the brakes from the coach batteries is so anemic, yet its usual forceful level from the tow vehicle.

But SteveH described just hearing the click of the magnets, like I did. I'd like to hear from others what they hear at their brakes when they can get someone to pull the breakaway pin.

[SteveH]

I'd go test mine for you but my brakes are now electric over hydraulic, totally different deal.

[Dan and Liz]

Are you sure the pin is the right one? There are at least a couple of designs for the plastic pins, and iirc at least a couple of lengths. In my case, the tip of the pin broke off and had to be retrieved with a hemostat.

[Siegmann]

Dan and Liz, it is actually a brand new Bargman Breakaway Switch, whose continuity I've tested. It's working and is not the issue.

OK folks, for those in or near their rigs, and resting up this Sunday, please (un-plug) and go out and pull your pin and tell me if you hear your brake magnets "click", or "clank and hummmm". We'll all get data on this question, and you'll have done an important safety test of your breakaway switch. Thanks--- Jim

[Jim & Susan]

Yer not supposed to hear that "hummmmmm". Lemme explain.

I went thru the exact same scenario last year when I changed out my break-away switch. Had good continuity, voltage was right, etc, blah, blah. Did many of the same things you're doing. Rewired stuff, bought parts.

The only way I found to test this was to do this:

Get one wheel (or in my case, one axle) off the ground. Disconnect shore power, disconnect umbilical from TV (this is very important because you might fry your controller if you don't). In my case, I unhitched from the TV as well, just so I could prove good ground in the camper internal wiring.

Pull pin and try to spin one of those airborne wheels. IT SHOULD NOT turn. If it does, you have some other issue.

Let me go and find my thread on this. Do yourself a favor and skip to the end .

Jim

[Jim & Susan]

Here's my story of woe. Skip down to post 13 for the answer.

http://www.airforums.com/forums/f464...ng-124450.html

Jim

[ROBERT CROSS]

Originally Posted by Siegmann

Dan and Liz, it is actually a brand new Bargman Breakaway Switch, whose continuity I've tested. It's working and is not the issue.

OK folks, for those in or near their rigs, and resting up this Sunday, please (un-plug) and go out and pull your pin and tell me if you hear your brake magnets "click", or "clank and hummmm". We'll all get data on this question, and you'll have done an important safety test of your breakaway switch. Thanks--- Jim

Just what I would do.....

Get a wheel off the ground, spin and have someone pull the switch just to make sure.

Our Classic really don't 'hum' much but the brakes work fine.

Bob

[Siegmann]

Jim & Susan, many thanks. I had spent 1/2 a day trying to solve that problem (that did not exist) and I've been worrying about it since yesterday afternoon. And special thanks to idroba and his explanation in that older thread. This forum is great!

[Seabloom]

Thank you so much as well. I too expected the hmmmm which was absent with the new switch installed. The one wheel up test proved to me that the switch and brakes were all working. This puts my mind at ease.

FYI don't pull the switch pin with the truck connected, my GMC brake module was unhappy for about 15 mins before it reset itself.