Trailer Brake Lockup Without Applying Tow Vehicle Brake

[haynestream]

We have a 2012 Flying Cloud 23FB and tow w/ 2011 BMW X5 w/ Tekonsha Prodigy RF Brake Controller. I've towed w/ this same setup for last 8 years. Last week, I towed about 15 miles from home to dump tanks and trailer brakes locked up 2 separate times about 5 minutes apart, and in neither case was I applying TV's brake. Event #1 - I was driving about 60mph on interstate and suddenly, there was enormous trailer sway. Looked in rear view mirror and trailer was fish tailing heavily. It was over in about 15 secs. Initially, I thought I must have done some "really bad steering" to create such a sway (actually, I accelerated to try to reduce sway....not a good idea in this particular case). Then, it hit me afterwards that this was the trailer brakes! They seemed heavily to near fully engaged. Then came Event #2. Fortunately, I was going slower since the lockup lasted longer. The car was for all practical purposes out of control, shaking violently. I thought I was going to be overturned - even the DSC warning illuminated on TV's dash. It was an intense 30+secs. I just took my foot off the accelerator and held the steering wheel straight. Got to dump station and drove back home without any further issues. I have tested the TV's 7 way pin and all functions tested correctly. I have ordered a replacement Brake Controller as well. Before I pursue my next options/service/repair, I want to get your thoughts on the possible culprit. Any ideas would be greatly appreciated. Thanks. Mark

[57Vintage]

Have you looked at the breakaway switch? Are those wires shorting or the housing compromised allowing corrosion inside.

[GCinSC2]

Mark,

Glad you are ok.

Were you able to determine if it was happening on all four wheels?

Can you pull wheels and drums and inspect brake hardware? Or at least raise trailer ans spin each wheel by hand and listen for normal drag brake drag sound or do you hear metal on metal screeching or parts rolling around.

Gary

[overlander63]

Originally Posted by haynestream

We have a 2012 Flying Cloud 23FB and tow w/ 2011 BMW X5 w/ Tekonsha Prodigy RF Brake Controller. I've towed w/ this same setup for last 8 years. Last week, I towed about 15 miles from home to dump tanks and trailer brakes locked up 2 separate times about 5 minutes apart, and in neither case was I applying TV's brake. Event #1 - I was driving about 60mph on interstate and suddenly, there was enormous trailer sway. Looked in rear view mirror and trailer was fish tailing heavily. It was over in about 15 secs. Initially, I thought I must have done some "really bad steering" to create such a sway (actually, I accelerated to try to reduce sway....not a good idea in this particular case). Then, it hit me afterwards that this was the trailer brakes! They seemed heavily to near fully engaged. Then came Event #2. Fortunately, I was going slower since the lockup lasted longer. The car was for all practical purposes out of control, shaking violently. I thought I was going to be overturned - even the DSC warning illuminated on TV's dash. It was an intense 30+secs. I just took my foot off the accelerator and held the steering wheel straight. Got to dump station and drove back home without any further issues. I have tested the TV's 7 way pin and all functions tested correctly. I have ordered a replacement Brake Controller as well. Before I pursue my next options/service/repair, I want to get your thoughts on the possible culprit. Any ideas would be greatly appreciated. Thanks. Mark

Welcome to the forum. When is the last time you removed the brake drums and inspected the brakes?

[BayouBiker]

I'm thinking along the same lines as GCinSC2. If all four brakes were applied, I wonder if the trailer would fish tail. The drag should just pull the vehicle to a stop.

If the brakes where fully applied, I would expect them to lock and for there to be skid marks and obvious tire wear/damage on the tires. Perhaps you can get more insight looking at the tires.

I am struggling to come up with a explanation for a way the controller might rapidly pulse the brakes in a way that would produce the described symptoms.

I think the most likely is a mechanical issue with one of the brakes and so I go back to GSinSC2's advice to inspect the tires and brakes to see if that turns up more information.

[drbrick]

I would double check the brakes and the breakaway switch before replacing the controller. I would also check the bearings (we do every two-three years depending on mileage). I have found that the breakaway switch does'nt take much of a putout to activiate the brakes (been there).

[AzAirstream]

Originally Posted by 57Vintage

Have you looked at the breakaway switch? Are those wires shorting or the housing compromised allowing corrosion inside.

X2 - It sounds like an intermittent electrical issue with the break-away system. I would go there first. Possible RF interference? An devices near the controller in the car?



Please let us know what you find. I have the same controller.

[fwjumper]

My best guess is a mechanical issue In one brake. Often, the bottom spring breaks, potentially allowing parts to dislodge, then wedging itself and locking the drum. If all 4 wheels locked, I can't imagine the violent swaying. In fact, applying the trailer brakes is one method used to control away in an emergency.

[davidlparker]

Like others have said I'm glad you and your vehicles are OK. I am not a mechanic but can offer these thoughts from experience. I have a TT (not an AS) several years ago lock up all four wheels on an Interstate highway at about 65 mph. It was sudden and I was surprised. Since all four wheels locked up simultaneously I stopped in a straight line. There were skid marks on the highway and the tries were slightly damaged, e.g., flat spots from being dragged along the concrete roadbed. The cause was the breakaway switch. I disconnected it and replaced it as soon as I could get off the highway and find a shop to do the work. It never happened again. I think your first area to checkout should be the breakaway switch and wiring associated with it.

I was lucky. the traffic was light and I was in the right lane. I also had a one tone dually that was a rather stout truck. Good luck and let us know what you determine.

David Parker
1993 Excella 30'
1989 Dodge D-350

[james.mileur]

" to create such a sway (actually, I accelerated to try to reduce sway....not a good idea in this particular case). "

Your instinctive reaction to accelerate was spot on for sway. Did you manually apply the brakes at the controller with the acceleration?

[Dingram/Colo]

The brakes are held open electrically, and close when current is removed.
Check the wiring connection under the wheel well, there is a connection leading to each brake, you may have a poor connection(s).

I had a single tire fail, changed to spare, and thirty five miles later pulling into town, the spare tire at the same location locked up peeling the rubber down to the threads within in a hundred feet.
Found the connection was loose at the wheel well, tightened it up, & found another loose connection on one of the other brakes as well.

[n2916s]

Um, maybe not so much. The trailers electrical brakes activate when current is supplied to the outward facing brake magnet. It adheres to the brake drum, the friction displaces the magnet laterally and a set of cams push the brake shoes outward.

Somehow the OP’s brakes had an uncommanded asymmetric lockup. A real head scratcher...

[GCinSC2]

Originally Posted by Dingram/Colo

The brakes are held open electrically, and close when current is removed.

Dingram,

Sorry, I disagree. Can you provide a link to a source that backs this up?

I personally made an inline brake circuit voltage and amperage tester. It connects inline between TV 7 way and AS. Pushing on the brake or actuating the slider applied power to the magnet actuating the brake.

Regards,

Gary

[BayouBiker]

Indeed, it had to be asymmetric to produce the symptoms described. The most likely seems like a single wheel problem.

[bibbs]

My vote: mechanical, Like others have said, an electrical problem would cause all the breaks to lockup with no sway. Inspect your drums, let us know, what you find.

[sirtate]

Originally Posted by GCinSC2

Dingram,



Sorry, I disagree. Can you provide a link to a source that backs this up?



I personally made an inline brake circuit voltage and amperage tester. It connects inline between TV 7 way and AS. Pushing on the brake or actuating the slider applied power to the magnet actuating the brake.



Regards,



Gary

If the brakes were held off by electricity, wouldn't they automatically lock when the trailer was unplugged?

You wouldn't need to chock the wheels to keep the trailer from 'running away' when parked, would you?

[overlander63]

Originally Posted by Dingram/Colo

The brakes are held open electrically, and close when current is removed.

That statement is totally false. You may be confusing electric trailer brakes with truck air brakes, which perform more as you describe.

[GCinSC2]

Originally Posted by sirtate

If the brakes were held off by electricity, wouldn't they automatically lock when the trailer was unplugged?

You wouldn't need to chock the wheels to keep the trailer from 'running away' when parked, would you?

Let's let Dexter Axle explain operation in this PDF https://www.dexteraxle.com/docs/defa...s.pdf?sfvrsn=2

If you raise a wheel to check a tire, bearings or brake adjustment it should spin "freely". Applying current thru the controller or if 7 way is disconnected pulling the breakaway cable pin for testing applies trailer battery power to the magnets for testing the breakaway circuit.

The magnets are not utilized for a parking brake function. The same PDF describes Dexters optional cable operated parking brake. Leaving the magnets energized would be a battery drain at the very least not sure if it would damage the magnets.

The Dexter website has a good document reference and video resources.

Getting to know how your brakes function, normal service requirements, adjustments and to your ability troubleshooting and repair can be the difference between a successful safe trip or something else.

Gary

[haynestream]

Originally Posted by overlander63

Welcome to the forum. When is the last time you removed the brake drums and inspected the brakes?

Right at 2 years ago - tires replaced, bearings and brakes fully inspected. As I left the shop, the shop owner actually said all brake components...even springs....were in great shape.

[sirtate]

Originally Posted by GCinSC2

Let's let Dexter Axle explain operation in this PDF https://www.dexteraxle.com/docs/defa...s.pdf?sfvrsn=2



If you raise a wheel to check a tire, bearings or brake adjustment it should spin "freely". Applying current thru the controller or if 7 way is disconnected pulling the breakaway cable pin for testing applies trailer battery power to the magnets for testing the breakaway circuit.



The magnets are not utilized for a parking brake function. The same PDF describes Dexters optional cable operated parking brake. Leaving the magnets energized would be a battery drain at the very least not sure if it would damage the magnets.



The Dexter website has a good document reference and video resources.



Getting to know how your brakes function, normal service requirements, adjustments and to your ability troubleshooting and repair can be the difference between a successful safe trip or something else.



Gary

My point exactly...

Either you apply current to the magnets to apply service brakes (requiring the trailer to be connected to a power source, in this case a brake controller), or the emergency brakes are applied the same way using trailer battery current through a breakaway switch.

Either way, they aren't automatic 'parking brakes' like seen on air braked vehicles with Westinghouse Safety Brakes (or similar).

If that was the case, the trailer would set its brakes when you unplug at the campsite. Just like a semi-trailer.
(Perhaps someone could design something like that?)

No chocks needed in that case...