Trailer Brakes not activating on 1995 Sunline T-1950

[cgandee]

Hi to all.
I had the trailer in the shop for getting a trailer fault on the dash of my F250. They found ground faults at 3 places and fixed them. However, I am still getting this warning and the brakes are not activating on the trailer. They cleaned the electromagnets on the brakes, but could they be getting weak and that is why the brakes don't grab. This is a 14 year old trailer.

[etkeeny]

did they adjust the manual adjusters on the drums while they were working on them? also did they isolate the trailer from the truck to verify the issue was with the trailer wiring not the truck? The first thing I would do is test the brakes using and external power source, like a battery charger, if you can't get the brakes to activate with the charger start looking at grounds, the chances of all four (i'm assuming a tandem axle) electromagnets failing at the same time is very slim. How does the connector look? any corrosion? if all of that tests fine check the plug at the back of the truck for voltage (with a volt meter) when you activate the brakes. if there is no voltage or very weak voltage start looking for broken or chafed wires. last question is is the brake controler factory or aftermarket? do you have another trailer or someone elses trailer you can plug into and check to see if it works?

Hope this helps,
Eric

[Steve Collins]

Magnets don't all go south at the same time. In fact, I have never heard of magnets failing.

What can and does fail is wires, connections, and grounds.

If it was my trailer, I would first find another TV and check the brakes with that vehicle's brake controller to either duplicate the condition or rule it out.

After that, I would go through the entire wiring of the brakes from the 7 pin connector on back. Every wire would get 100% eyeballed for breakage, chafing, or whatever. Every connection would get cut out and replaced with cleaned wire, dielectric grease, heavy-duty crimp-ons, heat-shrink and then tape. Every ground point would be replaced with a new grounding connector, cut back the wire to clean copper, dielectric grease, tightened down and then protected from corrosion.

And, as pointed out above, make sure the brakes are properly adjusted. They are most likely the old fashioned drum brakes with the manual star wheel adjuster.

There are several extensive posts here in Repairs and Maintenance about brake maintenance. Look back through and read them over for more details.

[cgandee]

Thanks for your reply. The truck brake controller has been ruled out since we plugged in another trailer and worked fine. That is when we found the ground wire problem. They replaced 3. When the trailer is off the ground and checked for brakes they work with no resistance. However, when on the ground they don't, and this is why the suspicion of the magnets being weak. It is likely they have never been replaced in 14 years. The 7 way plug is brand new and the wiring has been checked. I will also bring up the adjustment you mentioned to make sure that was done. Thanks again for your advice.
Carol

[Steve Collins]

Magnet replacements are extremely rare unless they are physically damaged.

It is virtually impossible for all four magnets to fail at the same time.

Any decent utility, horse, or RV trailer shop can evaluate the entire braking system. That part of trailers is pretty much the same regardless of the type of trailer (except for large horse trailers - different critter all together.)

Which axles does your trailer have? Dexters were predominant in the '90's for Sunline so that is probably what you have. Go to www.dexteraxle.com and you will find the service manual for axles and brakes. It gives complete info about maintanence and troubleshooting.

[etkeeny]

Originally Posted by cgandee

When the trailer is off the ground and checked for brakes they work with no resistance. However, when on the ground they don't, and this is why the suspicion of the magnets being weak.

This sounds like the shoes are out of adjustment or worn out, has anyone taken the drums off and inspected the condition of the linings? Brake shoes will wear out over time just like the ones on your car, chances are they have never been replaced in 14 years. I would remove the wheels and drums, inspect the shoes, replace them if neccesary, since the drums are off this would be the perfect time to clean, inspect and repack the wheel bearings. Put it all back together and adjust the shoes up so that when you spin the wheel by hand (while it's off the ground) it freewheels no more than 2 or 3 rotations before it stops. you want the shoes to barley be touching the inside of the drums but not so much that they drag heavily.

[frank]

Originally Posted by cgandee

Hi to all.
I had the trailer in the shop for getting a trailer fault on the dash of my F250. They found ground faults at 3 places and fixed them. However, I am still getting this warning and the brakes are not activating on the trailer. They cleaned the electromagnets on the brakes, but could they be getting weak and that is why the brakes don't grab. This is a 14 year old trailer.

Exactly what warning are you getting? And is this Ford's built-in controller? I believe JohnB has called it Tow Command.

If the controller is reporting a "fault", I would have to lean towards this being an electrical, and not mechanical issue.

If your controller is anything like my P3, a slight short anywhere in the braking system will cause a fault, and in turn, the controller will STOP applying power to the brakes. The P3 will also report a fault on an open connection, yours may as well. The actual fault you are seeing will be key to figuring out what the issue is.

If it is a short, it could be anywhere in the wiring, from the 7 pin connector back (since you report no issues with another trailer). All four brake magnets are paralleled into one wire for connection to the truck. Therefore, it would be imperative that all the wiring is given a very close inspection. Also, it has been reported several times that the insulation on the wiring likes to rub through INSIDE the axle tubes where the brake wiring is run on some models. Something along those lines could very well cause your problem, as the wire would see different "stresses" when the coach is up in the air vs. on the ground.

Apparently, another potential short point is due to worn magnets. I haven't put enough miles on any electric brake system to have experienced this issue first hand, but my "elders" assure me it can and does happen, and (most importantly) that it will be visually apparent that the magnet is worn to that point if you pull the drum and look at the magnet itself.

If an open, it could be a little more difficult to find. It is not unheard of that a conductor breaks inside the insulation and is then not (easily) visible from the outside. This would result in an intermittant open, which might cause a fault on your controller.

Again, the actual fault reported is going to be an important first step in figuring out where to start.

FWIW, I do feel your pain, I have an intermittant short in the brake wiring on my 2363. Despite eyeballing the entire system on two occasions, I can't find the location of the short. My next move is to completely rewire the brake wiring from the 7-pin back to each drum. It's easier for my sanity

Good luck! And report back and we will do what we can to help.

- Frank

[Lode]

My experience with this is similar to the other folks who've posted...

It's rare the magnets themselves will fail, it's almost always wire/ground related. The splice before it enters the brake assembly is sometimes the culprit, it get splash from the tires when it's wet, bleeding water down and corroding the inside of the wire, sometimes all the way to the magnet.... love those wire nuts!!! If you can't get a good splice down towards the magnets on those 2 wires, the magnets will need to be replaced.

If you are going to rewire, be aware that it needs to be a parrallel run to each brake as Frank indicated, don't use a series or your trailer brakes won't work as designed and you'll end up with more problems.

Hope that helps out and you can find the problem and get it fixed up.

Take care,
Lode

[Steve Collins]

Originally Posted by Lode

If you are going to rewire, be aware that it needs to be a parallel run to each brake as Frank indicated, don't use a series or your trailer brakes won't work as designed and you'll end up with more problems.

Lode makes a very good point. This is very important! If the brakes are wired in series on each side, that effectively means that each brake can not operate at more than half capacity at during full braking. If anything would perform like "weak magnets" on all four wheels, this would be one of the few possible scenarios.

[JohnB]

Hi cgandee

How did you make out? Still having issues?

If your getting a controller message on the dash, it sounds like you have a 2005 or newer F250 with the intergrated brake controller.

I agree with the others, a weak magnet is not normal. A shorted magnet or even more normal an unadjusted brake is very common.

You will have to sort out if it is mechanical or electrical or both. Could be both very easily.

For electrical, do you have a volt/ohm/amp meter? An amp check and an ohm check at 7 wire plug will tell a lot on the electrical. And further digging, an ohm check at the magnet itself will tell if it is shorted inside and or the wiring in the axle tube is brittle and touching ground.

For mechanical, have to pull the brake drums. Every 3,000 miles most TT brakes (which are non self adjusters, which is most all out there) have to be adjusted to take up the wear. If not, eventually you run out of magnet arm travel and you get no braking at all or close to it.

let us know if you need more help

John