DrewE wrote:
If your wiring is good (i.e. not shorted), you must see the same current at the magnets as at the brake controller. The electrons don't have anywhere else to go; current into a wire equals current out of said wire.
And yes, thanks to Ohm's law, it is impossible to have voltage and current controlled independently of each other for a resistive load. The laws of electromagnetism are most directly stated in terms of current, so the brake controller is eventually controlling the average current...but the average voltage has to likewise vary. Measuring the voltage at the controller and at the brakes would tell you what the voltage drop is between them, a very useful thing to check.
Do make sure that the ground return path is properly functional too.
I think I have spent too much time in the sun to read this correctly, something isn't right with the statement..
See if I can explain it better..
The sum of the RESISTANCE of the wire AND the brake magnets AND the voltage applied to the circuit will determine the exact amount of current drawn by the brake magnets..
If you were to connect a 12V battery directly to a brake magnet it should draw at least 3A at about 12.6V DC..
Four brake magnets should draw about 12A max..
Now, add in the wire from the vehicle to the brake magnets and you will get LESS than 12A for four magnets..
To further complicate things the current drawn by each magnet often is no equal due to the wiring resistance.. The magnets with the most wire will draw less than the magnets with the least wire.
To put it bluntly, if your brakes have gotten weaker, chances are the connections at each magnet have gotten corroded.
Pull apart each electrical connection and cut back the wire unitl you find shiny copper..
Many folk have often changed out the wire,upgrading the wire reduces the resistance of the wire. This allows more voltage to reach the magnets. This increases the current which increases the magnets strength.
Increasing the magnet strength will increase the braking strength.