Brake magnet scoring drum

Since the magnets are in parallel they will always have close to the same voltage on them. You will need to measure current through them to see any difference.

Get a multimeter with a DC (not just AC which is more common) clamp on current meter and clamp it to one of the lines feeding the magnets. About $40 on Amazon.


Place it far from the magnets or the mag fields will screw up the readings. Then measure the current to each magnet and see if they are much different.

I did the same as you and got complete new brake assemblies. Still could never get the two brake magnets to balance so I ended up rewiring them in series. That way they are guaranteed to have the same current. You have to turn the brake controller up to double the voltage
though to get the same braking action. Better I think than having imbalanced trailer braking on a wet slippery mountain road someday.

Another point is that once one brake is getting hot and burnished while the other is not it will always do more work so you will have to disconnect the hot one and do your burnishing stops with just the unburnished one to get it to work properly.

While you have things disconnect us a good time to get rid of the crappy insulation displacemebt connectors FR uses and replace them with real sealed butt splices or soldered connections.

If it's not getting pretty dang hot it's not working. The magnet runs on the drum when engaged so there will by design be some scoring.

If you have an IR thermometer measure the brake temps after a couple of stops using only the trailer brakes. A working drum will be several hundred degrees F and the drum paint will be out gassing if it's fresh. If one isn't working at all it will be nearly ambient temp.

Your strange current readings could be due to the pulse width modulation of your brake controller as it drops the TV battery voltage down. Try turning it all the way up and if that doesn't stabilize things then try a direct battery connection as you are suggesting. You can also look at the resistance of each magnet using the ohmmeter setting. Lippert has a spec for that in their manual.

At the end of the day you can do what I did, disconnect the hot brake temporarily, burnish the cold one, and see if it gets up to a similar temp once burned in and stops the rig ok. Then reconnect the two magnets in series, crank the controller all the way up, make a few stops. If you like the way that feels and both brakes are getting reasonably hot then go camping.

We all have to acknowledge that electric drum trailer brakes are 70 year old technology and will never work like we expect from our moderm sophisticated ABS hydraulic vehicle disk brakes.

Both magnets are within specs on amps and ohms.  A friend checked it out and suggested that the brakes were not adjusted equally for brake-in and with the initial adjustment the wheel (jacked off the ground) should only do about a half of revolution, then you need to drive quite a bit applying the brakes until they settle in.  Replaced the hub what was slightly scored and the associated magnet.  Right not the brakes are pulling evenly and I had no idea just how hot the acceptable temperature was for the hubs during brake-in.  Time will tell.  Thanks for the help.

I'll pick up an IR thermometer.  Just wish I could have had a definitive answer as to why the magnets are scoring the drums.  My thought is that a bad ground or loose connection might cause one magnet to be energized more than the other while the trailer is bouncing down the road.  Just don't know.