Trailer brakes weak

[mpolt81]

Please help. Bought used 28' enclosed trailer with weak brakes. Adjusted brakes but still no good. Brake shoes good and not glazed with no contamination. When I check each magnet individually I get 3 amps. But when I hook up more magnets it gets interesting. 1 magnet = 3 amps, 2 magnets = 5.3 amps, all 4 magnets = 9 amps(should be 12). Also, voltage drops as i add magnets. At plug with none hooked up I get 13.5 volts, all 4 hooked up I get 9 volts. Ground is good, I even hooked up 2nd wire from trailer to truck for ground. All connections test good throughout. Also seems the longer the brakes are activated the lower the amps drops. I assume the original 12 gauge wireing is causing it? Don't feel like rewireing whole trailer unless i have to. Any sugestions?

[Justin M]

take a pair of pleirs and hold them up to the magnets and have someone manually apply the brakes with the brake controller. If the pleirs stick to the magnet, they are good. If they dont, you have one of two problems. Bad ground, or Bad Magnet.

[JSchuricht]

If your dropping from 13v to 9v just by hooking up all brakes, your wire is too small to carry the current being drawn. Try running a wire externally from the controller to the brakes as a test, don't drive this way.

[FX4STROKER]

Originally Posted by Justin M

take a pair of pleirs and hold them up to the magnets and have someone manually apply the brakes with the brake controller. If the pleirs stick to the magnet, they are good. If they dont, you have one of two problems. Bad ground, or Bad Magnet.

yeah try the plier trick. The best way to test trailer brakes it with a battery charger cause you get a good 12v source. What is the shape of the magnet is it round or oval? You could aslo run a jumper wire to find if there is a short. Are you sure they are asjusted all the way out casue sometimes the rust makes it a serious PITA to adjust them all the way out. How did you adjust them. The best way is to adjust them till they wont move at all then back off a few clicks that way it pushes both shoes aginst the drum. hope some of this helps

[mpolt81]

I tried the compass trick and it worked. Engaged brakes and checked each one, when you get close the compass points to it, worked good. The only reason I don't think it's the magnets is I get 3 amps out of each

[mpolt81]

Adjusted till the tires locked and I couldn't turn the the adjuster any more then backed off a few clicks.

The magnets are oval.

I'll try to run individual wires to each magnet Tuesday and see what happens.

[djh]

Are the brakes hooked up in parallel? Looking at your measurements it seems to me that maybe 2 of the magnets are hooked up parallel, but the other 2 are in series. Also might want to jack the trailer up, activate the brakes and try turning each wheel individually by hand and see if you have a weak magnet. I have had some weird issues with those magnets before where I had one wheel that could still be turned by hand and when I replaced the weak magnet the braking was all good.

[mpolt81]

Good point with the parallel/series post, as I checked
the wires at the magnets the colors were correct and in parallel. But I never checked be sure if the wires were crossed under he trailer.

[FX4STROKER]

I thought It didnt matter which wires you hooked up the magnet to. thats why they dont color code them

Nevermind I get it

[mpolt81]

During further trouble shooting, I found that the hotter the wires got from the current the lower the amps would be. After taking a suggestion from above post, I ran wires externally and it brought my amps to 11. Not the perfect 12 it should be but since it's a 1992 trailer I assume the magnets are not working to 100%. I then decided to quit messing around and ran all new 10 gauge wires to a waterproof junction box centered between my axels. From the box to the brakes I also used 10 gauge wires all the same length. The brakes are now pulling a constant 11 amps at the trailer brake controller. The brakes will not lock up even when empty but it's good enough for me. When empty, the truck brakes so good you can't even notice the trailer being back there. We will see how it works loaded.