Trailer Brake Controller Wiring

[YotaBota]

I'm installing a brake controller, CURT, in the truck and they use two gauges of wire in the same run,,, why?.
The wires out of the controller are 12g but the power and brake wires supplied are 10g. I'm trying to find the logic in splicing 12g to 10g but am at a loss. Shouldn't the wire be the same gauge end to end.
TIA

 

[jcdammeyer]

How long are the wires coming out of the controller? How far from the end of those wires to the lamps.

 

[Susquatch]

Shouldn't the wire be the same gauge end to end.

I can think of 3 possible reasons.

1. Two or more smaller circuits being fed by a bigger one.

2. A system designed for a specific application that only needed 12g but then in a different application they had to increase the gauge to keep the total voltage loss within limits.

3. The bigger gauge was required in an enclosed space or inside insulated sheathing to keep the temperature down.

Remember that different resistances in series are additive. So adding a bigger gauge to a smaller one might stop the overall voltage drop from exceeding a limit. For example, it's perfectly normal to use a long 12G extension cord plugged into a 14G home wiring circuit for that reason.

Got a wiring diagram?

 

[YotaBota]

The wires coming out of the "Main Module" on the right are 12g and the wires going to the battery and the trailer connector are 10g.

So adding a bigger gauge to a smaller one might stop the overall voltage drop.

This may be a reasonable explanation since the wire splits to feed two or more brake modules

 

[YotaBota]

@jcdammeyer - brakes are separate from the lighting.

 

[Susquatch]

This may be a reasonable explanation since the wire splits to feed two or more brake modules

Yes. Looking at your wiring diagram confirms that for me.

 

[jcdammeyer]

The wires coming out of the "Main Module" on the right are 12g and the wires going to the battery and the trailer connector are 10g.


This may be a reasonable explanation since the wire splits to feed two or more brake modules

View attachment 68555

Odd how they went against normal DC convention and made Battery + black. Almost like the guy designing it thought he was working with AC and the ground (neutral) is white.
Just plain stupid.

 

[Chicken lights]

Odd how they went against normal DC convention and made Battery + black. Almost like the guy designing it thought he was working with AC and the ground (neutral) is white.
Just plain stupid.

That's automotive wiring.

Also ground isn't neutral in AC, automotive doesn't have neutral

 

[jcdammeyer]

That's automotive wiring.

Also ground isn't neutral in AC, automotive doesn't have neutral

I have yet to see a white wire connected to the negative post of the battery to the frame and black wire from the battery positive terminal to the starter solenoid.

The people who built that module made choices on wire colours and it was a stupid decision IMHO.

 

[Upnorth]

I have yet to see a white wire connected to the negative post of the battery to the frame and black wire from the battery positive terminal to the starter solenoid.

The people who built that module made choices on wire colours and it was a stupid decision IMHO.

I have seen that colour code with some solar controllers. Black was positive.

 

[Susquatch]

I've seen it before too. But fundamentally I agree with @jcdammeyer - it's a dumb choice. Just because another idiot did it that way too doesn't make it right.