Replacing brake magnets

I decided to check the brakes and discovered that a wire was broken, to the magnet on the right wheel.

While repairing the brake I noticed that the strands looked black, as though something had burned. I grabbed the DVM and discovered that I had an open circuit - the magnet should measure 3-4 ohms. Probably explains my reduced braking power at the end of last season. I forgot to check that out :-(

Of course now it's pouring rain, I have the exposed axle covered with plastic bags, no replacement parts, and only a vague idea of how to finish the job.

Hoping to benefit from someone else's experience:

1) Best price/place to buy replacement parts? www.dexteraxle.com looks good to me

2) The manual says to reface the armature (in the drum). Does that mean I should completely remove both bearings before taking it to a machine shop? Does everyone really do this when replacing pads or magnets?

3) How long can I get away with leaving the axle 'exposed' with the hub removed?

4) Anybody have a copy of the instruction sheet for replacing the magnets and/or shoes? Can't download that from Dexter.

5) Does it make sense to replace the pads while I'm at it? The right side is at 1/8" left, so I have 1/16" left to go, per the manual.

Thanks for your input. This board is my #1 TrailManor resource!

Hi Dan,
I believe we met at Holiday Hill Campground last summer. Hope all is well.

I had a similar problem with my brakes when I first got the Trailmanor. One of the symptoms was the light on the brake mechanism inside the Van flashing on and off while going down the road, indicating to me a bad ground or a broken wire.

I did some investigating with a Volt meter, found that I did in fact have a broken wire at the stress relief grommet that brings the magnet wires through from the axle area.

To repair it, I removed the stress relief grommet, cut, stripped and cleaned the wires at the break, twisted and soldered together then wrapped really well with electrical tape.

Brakes have been GREAT since I performed this fix.

It wasn't clear to me where you measured the magnet resistance, but if you were measuring at the ends of the wires, It might be a good bet to cut the wire on the magnet side of the stress relief grommet and recheck the resistance.

Good Luck,

Just finished the job today.

Replaced both magnets. Got the parts locally at a distributor recommended by Dexter Axle. According to the date code stamped on the magnets, they were originals. Probably didn't need to do both, but the manual said to.........

The manual also said to reface the armature surface (inside the hub). I showed a hub (drum) to the distributor and he said it was in great shape and that the magnet would seat to the slight "bump". Didn't even want to take my money for new drums, which I would have bought!

The Dexter Axle applications engineer answered all my questions, and sent instruction sheets (which come with the replacement magnets anyway). I was pleasantly surprised to get such a thorough, useful answer to a question I submitted via e-mail.

Along the way I learned how to repack wheel bearings, including replacing the inner seals. Found very slight damage to 2 rollers on the inner bearing on the driver side. Since it made it to Florida and back (maybe that's what did it) I decided to just keep an eye on them.

Took a 20 mile test drive on the interstate just to make sure my handiwork wouldn't go up in smoke when we leave for Indiana on Wednesday. The tires (inflated to the max 50#) actually heat up the most. The hub and brake drum were surprisingly cool. I'm beginning to think my "hotter on the curb side" axle temperature observations on the way to Florida were due to the sun shining on that side of the vehicle. I left the bearings out to dry in the sun and almost burned my hand on them later.

No rust problems from leaving the curb side spindle exposed for several days.

I intend to check the pads again at the end of the season and replace next spring, if necessary.

My Tekonsha Brake Controller manual says that trailer brakes are not self-adjusting. (drum brakes on cars adjust when backing up...)

I assume this means roughly annual inspection and adjustment would be appropriate?

[Bill]

I have just concluded a bad experience with TM brakes and Dexter Axle, the manufacturer of the axle/brake assembly. On about May 20, I was coming down a beautiful but very steep, switchback-y road in Arizona (rte 191, the Coronado highway, much of which is posted at 10 mph). About 1/3 of the way down, I felt that something was not right with the brakes, pulled over, and found that the tow vehicle brakes and the TM right brake were quite warm, as expected, but the TM left brake was cool. My controller, a Jordan Ultima 2020, measures and displays actual brake current, and it showed a max current of about 3 amps, rather than the expected 6 amps. Apparently one brake was disconnected or bad.

We limped slowly but safely back to Scottsdale, our base of ops. Once in the garage, I crawled under the trailer, disconnected the wires right at both brakes, and measured the magnet resistance with a digital voltmeter. The right brake measured about 4 ohms, as expected, but the left brake magnet was open circuit.

I called Dexter Axle, and they authorized a warranty repair. I made an appointment with East Valley RV Specialists, a large and reputable service shop, and approved by Dexter. I took the TM in, and they confirmed that the left magnet was open. They also found that the right magnet was badly worn, presumably from the added load of trying to do the entire braking job, and from the asymmetrical braking arrangement. Beyond that, they found that one grease seal was leaking, and both bearings were less than half loaded with grease. I called Dexter again, the East Valley repair manager explained to the warranty rep what they had found, and Dexter agreed to pay for repairs to both wheels. The job was done, I paid $316 to East Valley, and sent a copy of the invoice, along with the old magnets, to Dexter as requested.

Two weeks later, I got a letter from Dexter denying payment. The magnets were perfectly good, they said, and should not have been replaced. Now remember, both East Valley and I had measured the left magnet and found it to be open, and both of us had viewed the extreme wear on the right magnet. But Dexter, having guaranteed reimbursement, unilaterally reneged on the agreement, leaving me holding the bag.

I called Dexter and expressed my displeasure, and they told me that not only were the magnets good, but the failure was my fault because I hadn't had the brakes adjusted on the prescribed schedule! I'm not sure how this can hurt magnets, but they insist it is so.

After a half hour of arguing, Dexter finally agreed to pay half the bill for "customer relations", but I am still left with the other half - and a very bad taste in my mouth.

Lessons learned? First, the brakes do require manual adjustment, as Oilspot noted. The schedule says it should be done after the first 200 miles, and every 3000 miles thereafter. Do it, because Dexter will ask.

Second, beware of telephone authorizations. Dexter, in fact, offered to pay East Valley directly, which would have gotten me out of the loop and prevented this problem. However, East Valley declined to accept Dexter's promise, and required me to pay on the spot. Did they know something I didn't know? I don't know, but I have asked them. And I don't have Dexter's check yet. Will this be another "agreement" that falls apart? Stay tuned.

Bill