Craziest Electronic Brake Problem I've Ever Had - Need Help Please!

[trbostwick]

Ok, first, some background information. My friend, Frank, and I converted a 34' 1984 Airstream Excella into a mobile cigar lounge. We pull our airstream several times a week here in Charleston, SC, as we do various events around town.

Anyways, getting to the issue: about two weeks ago, while pulling the lounge with my truck (a 2002 Chevy 2500 duramax), we noticed the brake controller light intermittently flashing on and off and could feel the airstream's brakes engaging for about a half-second to a second at a time, and making for a very jerky ride. It would happen with such intensity that we would occasionally hear the tires squeal for the time the brakes were engaging. We hadn't gone far from my home, where we keep the lounge when we're not using it, so we turned around and hooked up the lounge to Frank's truck, a 2002 F-350 7.3. His is the primary truck anyways, and we'd only recently purchased the chevy to have as a backup truck. We didn't notice any flashing brake controller lights, nor did we feel the trailer brakes engaging, so we thought it was probably just a bad controller in the chevy and that was that.

Until about a week later when the same thing started happening with the F-350. If you look at the pictures on our website, you can see why having such a jerky ride going down the road is a huge hassle, as the humidor shelves fall down and everything has to be repositioned in the lounge, not to mention the fact that it's a huge safety concern as we never know when the brakes are going to randomly activate.

So we started troubleshooting. Knowing that it happened on two different trucks with two different brake controllers and two different wire runs to the female 7-pin connectors in the back, we were pretty sure the issue was somewhere on the airstream. The first spot we checked was the male 7-pin connector to check for corrosion on the pins. There was some, but not much at all. We cleaned it and moved on. I opened up the trailer to 7-pin cable connection to look at all the connections and make sure one hadn't gotten loose or corroded. All looked good, so we taped everything back up with electrical tape and zip-tied the cable connection to the airstream's frame just in case there was some kind of wiring issue within the cable itself that got activated when we went over bumps, etc.

So, after making these adjustments, we had an event to do at a local brewery, and we didn't really get a chance to test it. Trial by fire! Anyways, we hooked everything up to the F-350 and were on our way. Well, the airstream's brakes were still engaging randomly, so we took a drastic measure: we unplugged the 7 pin connector. Both of our trucks have sufficient braking capacity to stop the lounge, if we keep in mind we'll need a longer span to brake in. I had two concerns with it: 1, if we needed to stop in a hurry, we were screwed, and 2, no brake lights. It was, however, broad daylight when we left, and we justified to ourselves that this would only be a temporary (as in that-day-only) fix.

So, we continued towards the brewery, 7-pin connector unplugged. We were very cautious, but thankful that at least the brake problem wouldn't be occurring.

Except that after about a mile down the road, we felt the lounge's brakes engaging! Completely electrically disconnected from the truck, the brakes would still intermittently lock up!

So we pulled over again and plugged the 7 pin cable back into the truck. If we were going to still have brake problems, at least we could have brake lights and emergency braking abilities. And so we hobbled to the brewery.

At the brewery, I thought about what could possibly be causing the brakes to engage when the cable was disconnected from the truck, and it occurred to me: the breakaway switch could have an intermittent short! So, while we were setting up, we unplugged the the 7 pin connector and put the battery switch in off to remove power. Then, I disconnected power from the breakaway brake module, taped up the ends, and put the battery switch back in on. We have a heavy-duty hensley torsion hitch and two 10000 lb chains connecting the lounge to the truck as back-ups if the hitch fails, and since we were still troubleshooting, we figured we'd be ok to see if this solved the problem.

The event at the brewery ended, and we packed everything up to go home. The 7-pin plug was connected to the truck, and as soon as we started making our way out of the parking lot, before we got on the road, the brakes were locking up again. I knew that if the brakes were engaging earlier when the 7-pin cable was disconnected, they had to be getting power from the trailer batteries, so I turned the battery switch to off.

And that's how we got home without any jerking brake problems. It's not the brake controllers in the trucks. It's not the 7 pin cable. It's not the breakaway module. So, my question is, what in the world is causing this problem, and how do we fix it? I hate running long-term with patches, and I just want to fix this issue, but I'm at a loss. Is there anyone out there who can help me?

[J. Morgan]

1. You have a short circuit between the trailer brake circuit and a normally "hot" circuit, powered by;

A. The house battery
B. The tow vehicle hot line
C. Both of the above

OR;

2. Your breakaway switch is failing.

I would change the breakaway switch first.


Superat stultitia.

(I had a similar issue where the the trailer brakes had shorted to my running lights, everything was cool til the lights came on....

The short was where the umbilical entered the trailer)

[DougEW]

Sure it's not a mechanical brake problem ? Find the brake wires at the axle tap onto the 2 wires run that back to the truck with a light bulb to confirm where the problem is.

[87MH]

Are the brakes magnetic drum brakes, or has the unit been converted to electric over hydraulic disc brakes?

Lots of possibilities for problems if you have the disc brakes.

[J. Morgan]

If the light on the brake controller is coming on when the brakes apply, the problem is electrical, and it is either the break away switch or a cross to a "hot" circuit.

This will be true whether the trailer has electric brakes or elec/hyd brakes.

The light coming on on the controller is a "tell".


Superat stultitia.

[B00merang]

Proving once again that most problems can be solved in breweries....

[Towit]

Cut the two wires off the breakaway switch, but leave enough to reconnect if it is not the problem. Cap and tape the wires and so they don't short and give that a try first.

[AtomicNo13]

X2 on the breakaway theory. Its the simplest of all scenarios to troubleshoot and fix.

[jdalrymple]

The break-away switch should not be effected by the battery disconnect. Assuming a normal "factory" installation, the break-away should have it's own lead to the battery or some un-switched source.

By any chance do the trailer brakes activate with a turn signal? Just thinking of voltage sources in the umbilical that go on and off.....


Regards,

JD

[AtomicNo13]

Check inside the 7 way plug. There is a possibility of a stray little strand of wire from either the charge line or the brake line is shorting applying the brakes. This could explain brake actuation while the umbilical cord is unpligged from the tow vehicle.

[Gene]

The wire from the breakaway switch runs under the cover for the propane tanks and then goes back to the trailer. It may be covered with a protective cable covering. There may be a partial break in that wire and/or it may have been pinched by the propane cover causing a short. Normally the breakaway switch is off until it is pulled out closing a circuit that engages the brakes. If there is a break the wires may intermittently touch briefly engaging the brakes. Do not confuse that wire with the one powering the jack as that one goes directly to the batteries so the jack can work anytime.

Gene

[ijustlee]

Kind of a tough one! Do you have drum or disc? What exactly do you mean "breakaway module" is it just a switch or something electronic? Do you by chance have a electrical schematic diagram for the trailer and a Volt Ohm Meter? On a problem like this I'd start with a beer and trace the wires on the diagram to see where there could be any possible connection between the battery and the brakes. Or start drawing one of my own as I go. Oh, also I wasn't clear if the brakes worked normal with the trailer battery disconnected and the truck hooked up; and do they work normal if you operate the brake controller by hand? It seems like you might have a wire that is getting pinched as you drive, or maybe not. This could be fun.

[PeterTod]

Pretty much the same problem with my 1965 22' Safari. And thanks for the advice, I'll start with the breakaway switch as it is the original. Problem happened on the road and my solution was to scoot under the trailer and snip the brake wires. It worked. But I did not keep track (it was raining) of polarity. As both wires from the electric brakes are the same color (red) may I assume that it does not matter which wires get reconnected? Thanks.

[Lumatic]

Is the problem on all wheels? I had one wheel intermittently lock. Turned out to be a broken spring inside the drum.

[J. Morgan]

Polarity to the magnets does not matter. They don't care.


Superat stultitia.