Electric brakes ? - Diesel Forum

drbond · 08-16-2005, 08:03 AM

Well here is the setup.
2 axle trailer, 4 wheel electric brakes, truck/trailer setting on level ground, one axle of trailer off ground, 05 integraded brake controller set to 10 gain with manual lever locked on (max brakes).

I am measuring the voltage at the magnets and wanted to ask the people who have done this, what voltage should I be seeing? After the first wheel, I did this on all four, but was puzzled by the reading.

Thanks,
Bondo©

drbond · 08-17-2005, 11:00 AM

Ok, nobody ever measured this? I expected about 12 volts but only getting 1.2 volts at the magnets with full brakes applied. Not sure but I think it has to do with the controller sensing that the truck/trailer is not moving, so the voltage is less. Any ideas???

Thanks,
Bondo©

jeepman · 08-17-2005, 01:14 PM

From what I've read about the factory controller, you are right on track. The voltage comes up with the speed of the truck.

csd · 08-17-2005, 02:09 PM

I don't know about the integrated controller on the 05, but I can tell you all about my Jordon Ultima, and I suspect they should be similar.

I just went through what you are doing. The bad thing about electric brakes is that you can't see where the electrons are going like you can with the fluids in air or hyraulic brakes and air or hydraulic lines are less prone to break than are wires.

Brakes controllers control current, not voltage. When the brake controller is working properly and the magnets are all wired well, I see 13.5A going to 4 wheels or a bit under 3.5A per wheel when I press the manual emergency brake button on the controller.

The voltage at each wheel is whatever the controller needs to get that current through the magnets. On my trailer that takes 11V or so.

If you are seeing proper brake current (3+ amps per wheel) and it is only taking a few volts to do so, then there is a short in your brake system. My Jordon has a warning indicator code if you connect it to a shorted brake system. Not sure about the Ford controller.

One of the things I really like about the Jordon Ultima is that it shows brake current right on the controller. I know exactly what is going to the brakes without hooking up an ammeter. Other brake controller manufacturers could learn something from this. A reading of "10" on the output or 5 green LEDs doesn't mean squat. The current going to the brake magnets is what matters.

Now that I know 13A is the standard for 2 axle systems, I check the current everytime I hook up to a trailer. If I see 9A I know I'm probably hooking up to a trailer with a wiring problem.

I don't think the integrated controller will drop brake voltage based on speed, especially when the emergency brake button is pushed. I suspect, but don't know for sure that the brake current is totally proportional to the brake fluid pressure in the hydraulic brake system and the gain only sets how much current is provided for a given amount of brake fluid pressure. I'm just guessing here though.

If your brake wiring is good and you are getting 3A+ per wheel, you should be seeing 10+ volts at each wheel.

I don't understand the logic of getting an integrated brake controller if the manufacturer doesn't give you instructions on how to troubleshoot it. I can only imagine what a Ford dealer would do if you showed up at their shop with a truck and trailer and said "my brakes don't work".

drbond · 08-17-2005, 03:37 PM

Thanks for the replies. I know I had the Jordon in my 99 and agree it's nice to see the current supplied by brakes. Just puzzled by the low voltage but thought as well it was just because nothing was moving. I didn't want to measure current, as I didn't want to break the connections to insert my meter. AND I would never even think about taking it back to Ford with a break controller question/problem. They look at me funny now when I go in and ask for service, a diesel, nope don't service that, but I'll sell you a new one! At least they tell me up front they don't service it.

Bondo©

jeepman · 08-18-2005, 10:15 AM

Thanks for all the info on the amps and such. I was trying to find(for sure) the brake wire in the trailer plug at the back of my fifth wheel trailer(I have a hitch on it). In the past all someone had to do was push on the brake pedal and I could find it, but with this controller I couldn't. I'll try the emergency lever to see if that works. BTW, I've never used a Jordan controller but the integrated controller on this pickup is the best I've ever used. It's smooth, no jerking when stopping, you don't even know the trailer is back there. 13400# fiver.