Help with trailer brakes

My 09 F250 stated giving me trailer connection intermittent error messages.I tried cleaning the contacts but it gradually got worse. I replaced the trailer cable/connector back to the trailer junction box and have no more issues. We just completed a 2000 mile trip with no error messages.


Dick

lenr wrote:
When measuring the resistance of electric trailer bakes at the trailer end plug, you should get 4 divided by the number of wheels. I got 1.0 – 1.1 on my two axle trailer.

Since I only have two brakes that would mean my resistance should be 2 ohms. So I disconnected my brake leads from the wires, and substituted a 2 ohm power resistor. Checked that the terminals at the 7-way measured 2 ohms -- they did. Plugged into the truck and the truck tells me "trailer disconnected". Didn't fool it.

But I'm convinced I have flakey magnets. I rechecked the resistance right at the magnet leads. They have excessive resistance yet work on the road. My empty trailer locks the wheels where it's supposed to. I give up. I'll just replace the magnets and see where that puts me.

lenr wrote:
When measuring the resistance of electric trailer bakes at the trailer end plug, you should get 4 divided by the number of wheels. I got 1.0 – 1.1 on my two axle trailer. 28 is WAY too high for electric brakes. Although hydraulic over electric will be higher, I don’t have experience with them. My 2012 F-350 came with the brakes set to electric. You may have to have the trailer or a dummy plugged in to change the setting in the information panel—it doesn’t seem to come much alive without anything plugged in. I’ll bet the problem is with the trailer wiring. I’ve had the best success replacing ALL brake wiring—not trying to find where the problem is.

Thanks lenr. That sounds like what I would have suspected. I think the controller numerical setting is supposed to be the applied voltage, in my case around 6. So with 1 ohm resistance that would be a brake draw of 6 amps. My 28 ohm resistance would allow just a couple hundred milliamps. Not enough to work the brakes -- yet they work. I wonder if I have an intermittent bad connection where applied 6V can "burn-thru" corrosion or similar. I'm going to unwire the magnets and measure them directly. And if I just look for voltage drops across joint to joint it should be easy to locate the problem. If it's corrosion, I'll just replace it all. But I'm suspicious of a workmanship error. Trailers aren't built by master craftsmen.

By the way, the two plug pins to measure for brake resistance are the bottom two left and right of center with the key straight up.

When measuring the resistance of electric trailer bakes at the trailer end plug, you should get 4 divided by the number of wheels. I got 1.0 – 1.1 on my two axle trailer. 28 is WAY too high for electric brakes. Although hydraulic over electric will be higher, I don’t have experience with them. My 2012 F-350 came with the brakes set to electric. You may have to have the trailer or a dummy plugged in to change the setting in the information panel—it doesn’t seem to come much alive without anything plugged in. I’ll bet the problem is with the trailer wiring. I’ve had the best success replacing ALL brake wiring—not trying to find where the problem is.

Not so stupid a question as I didn't know there was an optional setting for EOH. I'll look thru the menu.

I installed new 7-ways on both.

We had that problem. It was dirt in the 7 pin. Took awhile, but it finally went away about the third time we cleaned it.

I have gotten those messages on my dash. I found that the female round plug on the truck was defective.

stupid question, but you do have your Ford brake controller set for electric brakes, not EOH ?

It's been back to the dealer twice. They haven't a clue. If you have a bulletin number or something they could look up?

EDIT, Yeah I just spoke to the local service mgr again and he hasn't heard of this, but he's going to make some phone calls. Thanks.