brake controller output

lenr wrote:
Whether the controller is controlling amps or volts is an interesting question. I always assumed it was volts. Amps is actually what determines the strength of the magnetic field but it should be directly proportional to amps.

I haven't ever checked a Ford, but my GM, Ram, and Prodigy controllers I've owned have actually controlled both voltage and current in a crude sort of way. What they actually do is send the full voltage from the Circuit breaker to the brake solenoids, but do so by switching on and off really rapidly. (Pulse Width Modulation) the frequency, or number of pulses per second stays the same, but the duration of how much of how much time during each pulse power is switched on varies (Duty cycle). Some millimeters, and all oscilloscopes that I know of can measure this for you, and with a scope you can see a graphical representation of the voltage waveform which is handy for visualizing what's going on. (Yes, I'm one of those guys who carries a pocket scope in the tool box of my truck)

If you have a newer RAM truck, the duty cycle maxes out at 65 to 66 percent, with Chrysler saying it goes up with speed. (My own testing says otherwise) My trailer brakes draw about 12.3 amps when connected straight to a battery, but max out at approximately 6.5 to 6.8 with the IBC on my truck. I'm still working with Chrysler to try to resolve this, but it causes inadequate braking to put it mildly. To add insult to injury my trailer brakes work fantastic if towed by my neighbors ford, or with a cheap aftermarket brake controller. How embarrassing ;-}