Wanted the dash to register one of my boat trailers which has surge brakes, with the goal being the mileage thing and getting the directionals to blink 5 times when hooked up.

This is a cut and past post I did on another forum and it has some additional things I found out.
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One of the key reasons for choosing The Ford over GM and Ram 5 years ago was some of the advanced features, mainly the trailer brake controller.
Ford uses a hydraulic sending unit in the brake system to give feedback for the TBC instead of the typical brake light circuit and inertia inputs. IMO this allows better control over trailer braking.
Other benefits are a hill hold feature, trailer anti sway, limited anti lock and a lane change blinker form 3 blinks to 5 blinks.

Note on anti lock, there is a contradiction in the manual.
Page 257
Avoid towing in adverse weather conditions. The TBC does not provide anti-lock control of the trailer wheels. Trailer wheels can lockup on slippery surfaces, resulting in reduced stability of trailer and tow vehicle.


Page 258
The TBC interacts with the brake system of the vehicle, including ABS, in order to reduce the likelihood of trailer wheel lock-up; therefore, if these systems are not functioning properly, the TBC may not function at full performance.

Part of the programming is a reduced output to your trailer brakes under 11 mph speed. This is to limit the "tugging" you may get in stop and go traffic.

Page 258
The TBC is equipped with a feature which reduces output at vehicles peeds below 11 mph (18 km/h) so trailer and vehicle braking is not jerky or harsh. This feature is only available when applying the brakes using the vehicle’s brake pedal, not the TBC.

So, I had a goal to have the dash monitor to "know" when my boat trailer was hooked up for 2 reasons, one so that the monitor would track trailer mileage, but mainly to have the 5 blink lane change feature. I made up this bulb and socket thing. It is wired into the 7 way's connector on the brake circuit. It will sit inside the trailer tube. With the resistance of the bulb the TBC now sees a "trailer" connected. Goal accomplished, TBC shows my Whaler 21 and the turn signal blinks 5 times.

What I found out was a bit on the TBC control. I did not measure voltage, just used a visual of the bulb. Activating the TBC's manual lever from off to max had the bulb glowing as you would expect, from off to very dim to full brightness. Stepping on the brake pedal was a different result. Just enough pressure to turn on the brake lights yielded no TBC output. More pressure, more light. Applying full pressure to the pedal and the bulb seemed to be only about 1/4 to 1/3 of full brightness. But, after 5-6 seconds the bulb came on full bright.

So an in the driveway only test; it would appear applying the truck brakes just enough to light the brake lights will not activate the trailer brakes at all, or in my case get the pump spinning to build up some pressure. This would explain why the Ford drivers may experience more off a felt delay with electric over hydraulic trailer disc brakes.

When I find another spare 7 way I will do the test a little different. I'll hook up another bulb with a voltmeter and go for a ride to see how it reacts. I should be able to do this with and without a trailer since my truck has two 7 way receptacles.

 

Duane, thanks for sharing your results !

 

Duane -
Thanks for doing the work on this...
I am curious on a couple of things -
1) Did you change the gain on the brake controller at all? That would make the light grow brighter-faster with the gain turned up - I would think. Not that it would make any other difference..
2) Since it is just the resistance of the bulb in the brake circuit, I would think that you'd be able to accomplish the same thing with a 1 watt 500 ohm resistor and have the gain turned way down so as to not overheat the resistor. You could also heat sink the resistor. Just thinking of ways to get away from using a bulb I guess.

 

Why not use a magnet from an old brake assembly? Or measure the resistance of one to know what size resistor to use.

I know several people that tie a brake magnet to the tongue of a trailer without brakes to trigger the mileage tracker in the truck.

 

Randy - The gain was left from whatever I had it set to last time I towed the 5th wheel, either 9.5 or 10.

I had the bulb and socket - a resistor would have required a trip to Radio Shack.

Turning the gain down with a resistor brings up another good point. How nice would it be if when you change trailers on the screen it also changed gain and brake type as well?

Spec - magnets old brakes - don't have any.

 

Interesting info!

thanks for sharing!