This will probably get moved to the mechanic section but thought i'd try to get some of you guys (who don't visit that section) to see this and maybe help me out. I bought a used trailer last year. tandem axle 3,500 each axle. It's a Big Tex trailer, year 2003. It came with electric brakes on the rear axle only. When i bought the trailer a year ago i also bought a Reese Pilot control box for the cab. I wired up the box correctly, even inserted the 40amp fuse in stud #1. im getting 10volts on the trailer brakes at the rear of my truck. But the box keeps telling me that there is no trailer hooked up, so my only guess is that there is not a closed circuit somewhere, correct? The box is putting out roughly 10volts when i squeeze the trigger, but it doesn't register any numbers on the display, only a little dot showing that it's hooked up. ive tested all plugs (truck and trailer) with ohm meter and they're good. ive gone all the way back to the brakes on the trailer. there' a black wire and a white wire (blackower white:ground) that run down the left-hand side (drivers side) of the trailer, once they reach the rear axle they get spliced with power going to the brakes on the drivers side then power and ground run from that splice across the trailer to the other brake. I cut the wires right where they were spliced, hit my brake pedal and tested, i'm getting 9.5volts of power. So i've deducted that I've got power to the brakes. OH, i forgot to mention, when i first started playing tinkering around today, i found out that something somewhere is crossed because the brakes were activated with no pedal or controller box. Then once i hit the brakes pedal the trailer brakes let up (freed up). So for a second it was reversed somehow, brakes applied = no trailer brakes and no brakes applies=trailer brake. But after i re-tested everything and hooked it all back up the problem went away. ??? THINGS I KNOW: 1. there are not power issues on the truck (2005 gmc sierra z71) 2. Both trailer and truck plugs are fine 3. Have good power and good ground all the way back to the trailer brake My Questions: 1. Why does the reese pilot box show no trailer connected, even before i cut into the wires? 2. How do i know if the electro magnet is good or bad? 3. there are two wires that go into the magnent, they are both green, how do i tel which is positive and which is ground, or does it even matter? 4. Was it a possible ground issue that cause my brake to be applied even though i wasn't applying the brakes? 5. Where do i go from here to figure this problem out? Thanks guy. OH and from the rust on the inside of the brake hub, the brake shoes aren't engaging, only the magnent is. So tomorrow i'm going to pull the whole brake unit off and tear it apart and beat the rust off and lube it and get them function i hope. I hope someone reads this and can help out. Thanks.