Recently bought a 1992 pace american enclosed 28' trailer but the brakes are weak at first then non existant. Readjusted brakes but still nothing. Brake shoes are good and not glazed. Here is where it gets interesting... Getting 3 amps at each of the 4 magnets when checked inividually. As I hook up more than 1 together in paralell the combined amperage drops. 1 magnet = 3 amps, 2 magnets=5.3 amps, 4 magnets=9 amps(should be 12). Also the voltage drops atthe same time. Getting 13.5 at plug but with all magnets hooked up I get 9 volts. Still original 12 Gage wire. Ground is good, even hooked up 2nd ground from trailer to truck. I'm assuming old wires went bad causing voltage drop? Any help would be appreciated.

 

I personally never had a problem with brakes. I have had problems with controllers.
I read someplace that the magnets can go bad. If i remember there was a test for that.

Could be moisture got into the wire and corroded it. I have seen some pretty snarly wires in my day from water. Due to its age wouldn't doubt it.. Running a new wire to the brakes might be in order. Here is the manual i had with my axles. Probably similar brakes on yours. Page 11 talks about the magnets.

 

Check the hub drums where the magnets grab 'em; if corroded, clean 'em up.

Steve

 

I have had problems with corrosion from sitting over winter interfereing with free movement of the brake parts. Sometimes a few repeated hits frees them up and sometimes taking them apart and cleaning is required. A fast check I use is to put a battery charger on the brakes through the normal connector momentarily while spinning a tire that is jacked off the ground. If brakes are free it should make a clunk and tire should stop immediately. If this works I used the same test using the brake controller with the manual switch and check each tire that has brakes individually.

 

What about the battery. Is it in good condition? Almost sounds to me like it is getting weak.

 

the brakes are powered of the vehicles electrical system. When running the alternator should provide plenty of power.

 

I had a set that acted goofy. Sometimes they worked, sometimes just a little and other times not at all. Turned out to be a chaffed wire from where the wire went through the backing plates to the magnets.

 

Check magnets first and then if those are working I will take controller to any trailer shop close to you and have them test that the controller is working properly

 

If the brakes are adjusted properly and the backing plates are not bent then replace the magnets.

But I am betting with 9 amps you have one brake not working at all, you can temperature check it after a short ride applying brakes as you go, ( if you have a temp gun)
one hub will be off temp from the other three, or you can have a buddy apply the brakes on the controller by hand, a compass held near each wheel will show what one is not working, the needle wont move at all, the others will cause the needle to swing towards the magnet if working, I have used it beofre but find it less reliable than a temp gun.

you should have 12 amps or more if all the magnets and brakes were working, being that you are at 9amps max, I would say one brake is not working at all, 6 amps 2 would be not working etc.

a drop in amps overall is an indication your magnets are failing but 9 amps makes it likely one brake /magnet is kaput

 

if bad battery causes an amp drop voltage doesn't matter as much

 

Well well well. Imagine that. Ohms law has been repealed. Thank you for letting us know that.

On the other hand, for those who actually do know something about electrical systems, the voltage drop is why there is a drop in the current. The voltage drop indicates an additional source of resistance somewhere in the circuit.

While it is ever-so-slightly possible for the resistance to be due to a problem with the wire itself, it is MUCH more likely that the resistance is a bad connection somewhere in the circuit.

Because the test results describes are consistent, it seems most likely that the problem area is one of the connections BEFORE the wiring splits to the different magnets.

The bad connection could be in the truck or the trailer but the first place that I would check is the weakest connection in the entire brake circuit -- the plug between the trailer and the truck. If either the pin or the socket is corroded, that is enough to create the kind of resistance described here.

The trick is to check the voltage drop ACROSS each connection. For some connection points this is easy, for other connection points it can be hard to find a good spot to connect the meter on both sides of the connection so you have to settle for checking the voltage to ground both before and after the connection.