Testing Emergency Break-Away Switch

[Steve Outlaw]

The other day I decided to see if my brakes needed adjusting and to test the emergency break-away switch on our trailer. I didn't have any reason to think it would not operate properly, but I figured knowing it would work would be better than finding out the hard way that it didn't. The trailer was not connected to the tow vehicle. It was plugged in to external power. I lowered the jacks on both sides until each tire could spin freely and pulled the switch pin. I then tried each tire and, to my surprise, they both still spun freely. No clicking, humming, no sound at all. My first thought was that, for some reason, it needed to be unplugged from the external power. No change. Next, I figured the switch or the wiring of said switch was somehow bad. I replaced the switch pin and checked the wires coming out of the switch. One wire showed 12 volts (this one apparently coming from the batteries) the other one was "dead" until the switch pin was pulled and then it too showed 12 volts. That proved that the switch itself was functional. I then found the blue wire inside the trailer that exits to the outside to attach to the brake drum on the street side. This wire tested hot when the switch pin was pulled, so I knew the wiring was good to that point. I then checked it outside the trailer at the drum and that tested hot also. Meanwhile, the wheels still spun.

So, what am I overlooking? Am I incorrect in my expectations? Could it be that the brakes only need adjusting? To the best of my knowledge the brakes have always worked properly thru the tow vehicle.

Any suggestions would be appreciated.

Thanks...

[BobB]

Do you have an effective ground from the brakes to the trailer battery? I've never tested the breakaway circuit in my trailer, to be honest. Most trailer brakes are not self-adjusting and require periodic adjustment. However, there are some self-adjusting brakes available and your Oliver may have them, for all I know. The simplest way to test trailer brakes is to turn up the gain on the controller until you get locking when the trailer brakes are applied manually while moving ahead slowly. Be careful not to make flat spots on your tires! If you think the brakes are not working properly, you might want to take your trailer to a certified brake shop.

[Bill K]

Steve,

I am going to be lazy. LOL

Since you have an Oliver I think you should have your manuals.

Find your axle manual and it should have a troubleshooting guide plus a lot of other information about the magnet and brakes.

I pulled my manual out and it had so much info that is why I said to get out yours.

Besides I am a hunt and peck typist.

Bill K

[Darwin Maring]

The way things work is: The switch applies power to an electromagnet that engages the hub and slowly applies the breaks. It Only Does This In The Forward Direction.

Take a compass and place it close to the wheel (But not to close) and see what the needle does then - have someone turn the switch on and the magnetism from the electromagnet inside the assembly should make the needle move.

Do the test with the TV connected and if it works then you can do it with the safety switch.

[Orlen Wolf]

The best brake test is to measure the current through the electromagnets. Just verifying that there is a voltage available at the brake assembly isn't enough.

[Steve Outlaw]

Brakes Fixed!

The problem was simply that the brakes were not getting a ground when not hooked to the tow vehicle (I've yet to make sure the brakes work during tow, but I don't have any reason to think otherwise--but I will check.) Both drums are grounded with the same wire (goes across to the other side thru the axle) so when one worked they both did.

Thanks for everyone's help

Steve

[Darwin Maring]

You now have a serious problem because the breakaway switch is used to set the brakes when the egg breaks away from the tow vehicle and when that happens, according to your post, you will no longer have a ground connection to the brakes.

[Dan Meyer]

Do you have a good on-board battery that is connected to the breakaway switch?

-- Dan Meyer

[Steve Outlaw]

I was not I was not clear in my post about having fixed the brake problem. The problem was simply that the ground wire attached to the brake system had lost its connection. We had an axle upgrade last fall and maybe it occured then. At any rate, I ran a new ground wire to the brakes and that solved the problem. Now everything works as it should. The brakes had always worked fine under tow because the ground was being supplied by the vehicle. It was only when I tested the system unhooked from the Tahoe that I discovered the problem. At first I thought it was not getting power from the on-board batterys or that the switch was bad, but all that tested OK. The only thing left to be wrong was the ground, and so it was.

Thanks everybody for your input and advice.

Steve

[RXN]

Hey Steve, Its looking like I may have the same issue on my Boler. I put a hitch on my 65 chev and wired it all up, everything worked, put an electric brake box under the dash, it works. Today I hooked up the break away switch, It doesn't work. I'm guessing our set ups would be the same, One wire off the break away switch goes to the electric trailer brake wire, the other wire off the break away switch goes to the positive terminal of the battery.

Now you mentioned it was your ground, Did you still have the breaks engauge when the brake pedal was applied? or the brake control lever of the electric brake box? that stuff is working fine on mine. So if the ground was bad would that affect those systems as well?

I'll have to crawl back under tomorrow and check ground.

[Kenny Strong]

When checking mine, the first thing I was doing, was to listen for the magnets to make a clicking sound, when they are engaged. I cleaned the ground point on the frame, all clicked well and worked well.

[RXN]

I had no volts to mine, turns out the + & - wires were reversed at the battery. All is working now