Should I Upgrade Brake Wiring?

[Yoda]

As my trailer belly is wide open and I can get to all the wiring, should I upgrade my brake wiring size? I think it is 14 awg (same as everything else), so say upgrade to 10 awg with the bigger brakes that will come with the new axles? My existing brakes are 10 by 2.25 and the new ones are 12 by 2. I am assuming the magnet is bigger on the 12x2 - is that correct?

Thanks for your thoughts

Keith

[Cate&Rob]

Hi Keith,

I would think that 14 ga is more than sufficient. Magnets are all the same (as far as I know). What you might want to check is the gauge of the wiring coming through the axle tube to the other side. In OE installations this is often a much lighter gauge.

Rob

[Yoda]

Hi Keith,

I would think that 14 ga is more than sufficient. Magnets are all the same (as far as I know). What you might want to check is the gauge of the wiring coming through the axle tube to the other side. In OE installations this is often a much lighter gauge.

Rob

Thanks Rob

Is it safe to assume Dexter would get that wiring size correct as the axles come pre-wired through the tube?

Keith

[TedS]

I'd leave it as is. The magnets draw only 2 or 3 amps, each. 8 to 12 amps total in an emergency brake application for dual axle set up.

[Cate&Rob]

Thanks Rob

Is it safe to assume Dexter would get that wiring size correct as the axles come pre-wired through the tube?

Keith

Easy to check when you get the new axles and easy to pull new wires through if the OE wiring is less than 14 ga.

Rob

[Jlawles2]

New axles come with wire through the tube and connected on both ends to the magnet wires (at least in my case).

Honestly it would be quite difficult to add wire if not done at the factory due to both ends being sealed. I don't thing there is much room left in the pre drilled hole for bigger wires either.

[Scott'n'Wendy]

Nope. No real gain to be realized.

[Yoda]

Just an update
I ran across this video on the effect of wiring size/voltage drop. Pay attention to the length of cables. My runs are probably 2x what he used and twice the brakes
https://www.youtube.com/watch?v=8dt11D0am6Q
To convert the wire size he mentions
https://www.electricalcarservices.co...le/c-p-0-0-520

So more food for thought. I just need to get under and verify the wiring sizes and check to see how difficult it will be to pull new wires through the existing harness from the pin box. It may be more of a pain than it is worth.

BTW one question - would you consider this 12V brake circuit to be non critical or critical per the Blue Sea chart? My gut says critical, but I have been wrong before.
https://www.bluesea.com/support/arti...r_a_DC_Circuit

What I cant find is any information on the magnet performance at varying voltage, or when I wold see max amp draw other than for short periods of time. Maybe in a break away situation.

Keith

[Cate&Rob]

It would be interesting to put a voltmeter across the brake apply wires to see the brake controller output voltage at different gain settings and brake apply pressures. You would think that someone would have done this . . . but, I can’t find it.

And . . . we are dealing with 1950s (70 yr old ) trailer braking technology.

Rob

[Yoda]

It would be interesting to put a voltmeter across the brake apply wires to see the brake controller output voltage at different gain settings and brake apply pressures. You would think that someone would have done this . . . but, I can’t find it.

And . . . we are dealing with 1950s (70 yr old ) trailer braking technology.

Rob

I may just do that if I have time once the new are in place. Set the initial gain different and just measure while DW runs the manual control o and hits the brake.

I have verified the wiring is 14 awg, but also discovered the connectors GD used UGG 7 pin wiring is 12awg.

Knife connectors were used. I have had several of theses come apart in other locations. Red sheathed 2 pair wire is 14 awg. Sheeting is specifically marked for brake wire - is that special? Could a WAGO connector be used here instead? It appears GD is using them on the new units, but don't know if they are using them on the brake wiring. The two white wires run down to the front drivers side brake.

At the pin box I found this - another knife connector. Right blue wire is from 7 pin and is 12 awg. Left blue wires runs to front bay and is 14 awg. I believe it runs into the sheeting somewhere there and the white wire is grounded. Center black wire is power from the disconnect switch from what I can tell. I definitively need to install my new pin 7 pin cable. https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

Note - the power feed in the 7 pin is 10 awg and is connected to a 14 awg that goes to the power bar-red wire nut foreground. Maybe I should fix that while I am there. But I do have My DC-DC now.

Another can of worms to work on.

Thoughts?
Keith

[TedS]

Before you connect wires to the brakes measure the magnets' resistances. Then you can calculate the amp draw for various voltage drops across the magnets. I = V/R. Current = voltage divided by resistance.

[TedS]

As a side question, what does the brake controller gain do? Gain what? Increase applied voltage? Increase delivered current(not likely) or allow more current to pass through?

[Yoda]

As a side question, what does the brake controller gain do? Gain what? Increase applied voltage? Increase delivered current(not likely) or allow more current to pass through?

Good question - lots of information out there on it. The way I was told, its the initial starting voltage when the brakes are first applied, then the voltage ramps up based on TV braking effort. What I don't really understand is on my Ford I have a second setting for low, medium, and high braking effort. Its a separate setting from the gain. I have wondered what that does - maybe it is the profile that the controller uses to increase the voltage based on the TV braking effort, but I don't know either. More to learn

Keith

[Cate&Rob]

Hi Keith,

Wago connectors are easy to use, but are not waterproof. I don’t think using these in a wet location would be a good idea. The Scotchlock “knife” connectors are waterproof and are widely used. Going “back to basics” with heat shrink wrapped soldered connections might be the best alternative. I have done these with a dab of silicone between the parallel wires of a 3 way connection and then heat shrink over the three.

Connections through the Weather Pack connectors that you have, are 100% weatherproof . . . even submerged. Full disclosure . . . I was party to the cold weather validation of these connectors . . . many years ago . . . (I use these everywhere that I can !)

Rob

[TedS]

Well, I went down the rabbit hole. It looks like brake controllers control voltage to the brake circuit. So if voltage is controlled, what is the associated current?

wire gauge. Ohms/30ft.
14 0.0758
12 0.0476
10 0.0300

Magnet Ohms. 4.0

Ohms per mag + wire
4.076
4.048
4.030

amps/volt/magnet
0.245
0.247
0.248

4 brakes × 0.245 × 6 volts = 5.88 amps
4 brakes × 0.247 × 6 volts = 5.93 amps
4 brakes × 0.248 × 6 volts = 5.95 amps

Double the voltage to 12 volts, full power out of the controller, double the current.


So what? Current per magnet per volt applied varies only in the third decimal. Not much current difference between the three wire gauges. Current through the magnet determines it magnetic strength. Doesn't seem to be enough difference to justify rewiring 14ga.