Troubleshooting Trailer Brakes that are Adjusted that Feel too Weak

Question:

I installed three pair on a 21,000lb tri axle trailer. The drums are used with both wear surfaces machined. The brakes have been on for a while but did not self adjust. I manually adjusted until the brakes dragged and then backed them off slightly. I figured they didnt need to be perfectly adjusted because they would self adjust. Im now well over 30 stops after adjustment and although the brakes are stronger they are still very weak. With the controller set to 10, only the passenger front tire is capable of reliably locking on gravel or wet grass. No tires will lock on pavement with an empty trailer. Reading voltage I have 11.2v in a junction box at the front of the trailer. Im reading 15.4a for all six brakes. Reading the amperage at each brake gives the following: Df 2.5, Dm 2.4, Dr 2.3, Pf 2.3, Pm 2.4, Pr 2.3. I believe these should be reading around 3 amps. Knowing the voltage was a bit low I tested the brakes using a fully charged jump pack and found their performance didnt improve and the amp draw was still at 15.4. I tried testing one of the old brake magnets and found that it pulled 4 amps and then tapered off to stabilize on 3.3 amps. Im at a loss as to what the issue could be as the amp readings are so consistently low.

asked by: Tim

Expert Reply:

When people have the issue you are describing what we typically find is that the wiring for the output circuit is too thin and it just can't carry the amperage needed. So you can check this but I'd suspect you have a thinner gauge wire than 10 gauge and you will end up needing to replace all of the wire with 10 gauge like part # 10-1-1 which we offer by the foot.

expert reply by: Jameson C