2nd Gen Non-Engine/Transmission 1995 3500 C&C trailer brake wiring?

[captndavie]

So I picked up a 1995 Cab and Chasis 3500 with a dump bed and am having the typical headlight switch melting and my brake light switch has also melted. I believe it could be in the wiring of my existing brake controller that has damaged the brake wiring plug and am trying to figure out how others have wires in controllers on these earlier models that don't have the pigtail for a brake controller. The manual shows a trailer brake provision but I'm not sure what I'm looking for and where to find it.

 

[brucejohnson]

captndavie,

I assume you have an electric brake controller with 4 wires coming out the back. What brand and series, if available.
I recommend you start by looking at how the truck and brake controller are wired together.

The controller should have: (Usual colors)
1. Brake Controller Power Wire - Supplies power to the brake controller circuitry (Black?)
2. Ground Wire - Circuit ground (White?)
3. Brake Sense Wire - Lets the brake controller know it's time to wake up and do its designed thing via the switched side of the brake switch (Red?)
4. Brake Signal Wire - (Light Blue?) - Sends the variable brake power to the brake magnets.
5. The electric brake provision may be tied/taped to the wiring harness bundle coming into the truck via the bulkhead connector. It should already be used if the installer knew what they were doing. If not, they would have run a separate wire through the firewall. Look for a light blue wire under the left side of the dash.

The melting of the connectors usually means the circuit has been overpowered with too many light bulbs. A Trailer Tow Relay (see your wiring schematic) is often used to energize those lights in order to lighten the load on the truck's wiring/connectors, which was designed to handle only those built in the truck's lighting plus small margin for a trailer.
If it is a small extra load due to only a couple of lights on the trailer, it can function for short periods of time at the added load.
If the trailer, or accessory tied into the lighting circuitry has excessive multiple bulbs the current draw may exceed the designed factory wiring. The connectors have some resistance so end up dropping voltage and, in turn, create heat to the degree of current flow causing a meltdown.
The brake controller power sense wire should only detect the activation of the brake pedal which does not draw much current. So, I would not immediately consider that circuit.
The light blue wire will have a variable current passing to the magnets through the brake controller and sensors while braking.
I would check to see if the wiring is properly connected to the Power Distribution Center which does have the load reduction relay. Check the PDC to ensure the relay is present and in use.
If the brake controller installer bypassed the relay, and the trailers that were connected to the system were loaded with multiple clearance lights, stacked/multiple tail/stop lights, accessory lights you have a guaranteed meltdown. This is where the brake switch gets involved, too many brake lights added to the truck's brake lights passing through one itsy-bitsy switch.
Hope this helps.

 

[Topzide]

@brucejohnson, I think that your colors are close, Black would be power hot, White would be ground in 12 volt systems, Red is the sense wire from brake light switch and Blue is the control wire going to the break-away box then to the brakes on the trailer.

The best thing to do on a trailer with the lighting, is to change over to LED bulbs/lighting to help with the power draw on the circuit. You can add a bunch of lighting to a trailer with LED for the power draw of a single 1157/3157 bulb! My 16' car trailer looks like a "Christmas" tree going down the road. Have had to many "idiots", try to merge into lane with it, especially when darker outside!

 

[brucejohnson]

@brucejohnson, I think that your colors are close, Black would be power hot, White would be ground in 12 volt systems, Red is the sense wire from brake light switch and Blue is the control wire going to the break-away box then to the brakes on the trailer.

The best thing to do on a trailer with the lighting, is to change over to LED bulbs/lighting to help with the power draw on the circuit. You can add a bunch of lighting to a trailer with LED for the power draw of a single 1157/3157 bulb! My 16' car trailer looks like a "Christmas" tree going down the road. Have had to many "idiots", try to merge into lane with it, especially when darker outside!

Thanks for the color correction. I questioned my source, maybe myself ...hence the "?". Then the truck wiring full of "colorful zebras". I shall fix the error of my way... Then there are the aircraft electronic circuits where white or red are power and black is ground. Oh, the challenges...in keeping the magic smoke in the wires.
Yes. LEDs are the way to go for trailer lighting, especially those with the Christmas tree effect, and older vehicles without the load relay built in. I have converted all my trailers to LED just for the better light emitted.
I am tempted to put a couple extra side marker lights in the middle of my travel trailer for the same reason, merging or changing lanes at night. Darned tailgaters. Some people seem to only focus at one point three feet in front of their vehicle and think they are the only ones on the road.

#ad

 

[Topzide]

@brucejohnson, Agree on the miss mass of wiring colors!! One spec here another one here and so on!

I've found those 3/4" LED marker lights are great. Plenty of light in a small package. Also went to the work bench and made up a set of convertors that allow a high and low light output! Allows me to wire to the turn signals, for a lot of bright light flashing to let you know my intentions. Full voltage for the flash and slightly lower for the marker. Have numbers somewhere on the resistor values.

Standard trailer wiring code
White Wire - Ground
Yellow Wire - Left Turn/Brake
Green Wire - Right Turn/Brake
Brown Wire - Tail Lights
Blue Wire - Brake Controller Output
Black Wire - 12 Volt hot lead
Purple Wire - Reverse Lights or Auxiliary Circuit

RV Industry code
White Wire - Ground
Red Wire - Left Turn/Brake
Brown Wire - Right Turn/Brake
Green Wire - Tail Lights
Blue Wire - Brake Controller Output
Black Wire - 12 Volt hot lead
Yellow Wire - Reverse Lights or Auxiliary Circuit