Brakes Grabbing

We just finished a 6 day trip, traveling from the Twin Cities area in Minnesota to Mountain View, Arkansas. Two adults, 3 boys and a small dog. We are driving a 2000 Honda Odyssey minivan, pulling a 2000 2619 TM. Yes, the Equalizer hitch was indispensable.

We drove down in rainy weather, parked for 4 days, then started back. On the first day back, the brakes on the TM seem to "grab" for most of the day. I'd start pressing the brakes, around 0.7 volts on the Odyssey Brake controller, the brakes would grab quickly, then with more pressure, fail with the SC (short circuit) code. This happened most of the day, so I was driving carefully, leaving plenty of room in front of me. The brakes never actually locked up, and I couldn't tell if it was one side or the other on the trailer.

Oddly enough, the second day of driving yielded no problems. The brakes were fine.

So my question is, could a pebble, or rust, get inside the brake mechanism and jam it up? We were doing some bumpy roads near the end of the first day, so perhaps "it" fell out.

Can someone give me a short explanation, or link, to explain how the brakes work? Are these magnetic, or just electric brakes?

Thanks in advance!
Dan and Cathy

[commodor47]

The brakes are electromagnetic. An electric current activates an electromagnetic which in turn causes the brake shoe to engage the inside of the drum.

Based on your camping trip description, it sounds more like a short in the wiring leading to the brake magnet. Check out the wiring underneath the TM, leading to the brakes. Check the wire nut connection . . . water may have entered the connector. I would definitely have the brakes inspected to rule out other possible problems.

The brakes are electrically operated, but the electricity energizes a magnet that tries to adhere to the inside surface of the drum. (This is the flat surface of the drum not the braking surface.) In doing so, the magnet pulls on a lever and the lever operates a square cam which spreads the brake shoes. When you adjust the brake controller you are varying the amount of current to the magnet so it is either a stronger or weaker pull giving more or less braking respectively. Short story, the brakes are electically operated mechanical brakes.

[Bill]

A short in the wiring would make the brakes weaker, not stronger, because it would divert some of the current that would otherwise go into the magnets. I can't think of any wiring failure that would make the brakes stronger or grabby.

On the other hand, the "Short Circuit" failure does sound like wiring. I don't know anything about the Odyssey brake controller, so I would be guessing. Bottom line, I'm not sure where to go with this.

What else could do it? Well, your theory about a pebble could be valid, though it would be hard for a pebble to get inside the drum area and get wedged. And it wouldn't cause an SC error. My money would be on rust - did the brakes actually get submerged in a deep puddle as you travelled? Either of these could make the brakes grabby for a while, but neither would cause an SC error.

Better explanations are eagerly sought!

Bill

I meant to address that problem, too, but got wound up with the description on how the brakes work. I would check the brake wires - specifically on the axle leading to the brakes. I would suspect a loose or corroded wire nut - not a short. An open circuit on one of the wires to the brake magnet on one side could cause the brake on the other side to be "grabby" since it would be getting all the current that would usually be split between them causing it to grab. I don't know if an open circuit would give you an SC error, but suspect it would since it would sense a change in resistance from two magnets down to one. I haven't done it yet, but I plan on getting rid of the wire nuts and soldering all the connections and putting shrink tubing over the joints. They make shrink tubing with glue inside it so when it shrinks the glue melts and makes a waterproof seal.

[Bill]

With respect, I still have to disagree. The brake controller does not "force" a certain amount of current down the line. It simply lets each magnet accept current proportional to the voltage applied by the controller. In other words, if the wire to one magnet opens up, the controller doesn't "force" two magnets' worth of current into the one remaining magnet. If one magnet goes away, the other magnet continues to see the same voltage, and continues to draw the same current as it did before.

After some more thought to try to reconcile the symptoms that Dan and Kathy described, I'm starting to look at another kind of wiring fault. If the brake wire is intermittently shorting against a 12-volt supply wire, this would cause the brakes to suddenly and intermittently apply, resulting in the grabby feeling. It would also confuse the controller, which would respond with some kind of error code (or perhaps be damaged).

This kind of short circuit would not happen under the trailer, since the brake wire and the 12-volt supply wires are in separate locations. The most likely place for this fault to occur is in the car half of the Bargman connector, where 7 hefty wires are crammed a space the size of a walnut.

It is common to find that the back of a Bargman connector (towards the front of the car, where the wires from the car enter the connector) is poorly water-sealed. In the rain, the tires throw a lot of high-pressure spray against the entire rear bumper area, including the connector. Unless the connector shell is terribly well sealed, water is forced along the wire bundle and into the shell. Once inside, it gets all over the connections and corrodes them, breaking some of the small strands that make up each wire. It would be even worse if the water is salty, as it likely was in the upper Midwest when you travelled. I bet if you opened up the Bargman connector shell, you would find water and/or corrosion in there.

By the way, the Bargman should have the open end angled slightly down, so any water will drain out of it. If the open end is angled up, water will pool inside.

As another thought, the problem could also be in the controller. It could have a fault that intermittently applies full braking even when it is not called for. But I think this is less likely.

Bill

Sorry, I've had family in town and have not been able to reply.

This is a great discussion. We were not submerged in water, but it was a heavy rain storm in Iowa while we were heading south. I'll check the wiring and connector. The connector is new though, but water would spray on it.

Do I pop off the wheel and drum cover to see the inside brake mechanism? I plan to have this professionally looked at, but while I'm working on the camper on my driveway, I could take a look. (We broke the table while camping, as I'm sure many people have.)

Thank you all for your help.

Dan

To see the brakes you will have to remove the drum (there is no "drum cover")- remove the wheel, remove the axle cap, flatten the locking washer tang against the spindle, unscrew the nut, take out the outer bearing and washers, remove the drum.

i want to replace the brakes on my 2004 3023 TM. Do they make a complete kit for both sides and if so, which ones do i buy? thanks, jeff

On a scale of 1 to 10 for mechanical knowledge, I'd probably be a minus seven, but I'd be surprised if an '04 TM needed to have the brakes replaced. Have you checked for wear yet? I'd do that before spending money and if the brakes are grabbing, I'd check how I had my brake controller set and also check to make certain that no grease has gotten in there. - Camp2Canoe