Old brake controllers somtimes no longer apply maximum voltage to the electric brakes.
electric brakes are designed to "lock up" if they are perfectly adjusted, at 8 volts on the magnets.
Adjusting electric brakes is rather simple, but most of the time, owners don't do it.
The adjuster should be tightened until you cannot pull the tire through with two fingers
, not all five fingers. Then you back off the adjustment 3 to 4 notches. That adjustment procedure works very well, unless, there is another problem.
You can also measure the voltage at each brake magnet, by having someone hold the controller at maximum.
CAUTION] DO NOT MAKE THIS TEST BY PULLING THE BREAKAWAY SWITCH.
If the drum surface is true, then an old drum should work as well as a new one.
Most often, we find a problem with the controller, the connectors or the wiring, both within the tow vehicle as well as the trailer. Each electrical connection should be confirm, not assumed.