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I want to use a 7 prong connector in a four wire trailer connection. I always have to rewire my trailer mid winter when I use the four wire flat connection. I am using a standard wire harness on my 90 Chevy truck to get the four wires from the truck to the 7 prong connector for the trailer. I have connected it with the pattern provided by the connector instructions. I figured white to white, brown to brown, yellow to yellow and green to green, would give me the same connection as a four wire connection and have the strength of the seven wire connectors.

I don't get the running lights to work , and they did before. The right turn also blinks the left turn when the lights are on. I have good grounds from the truck side of the trailer wiring harness and on the trailer side as well.

My question is, does the 7 wire connector have some internal connections between the prongs or are these just straight wire to wire connections?

And should the trailer be hooked up while I am doing this rework?

They sell a 7 pin to 4 pin adapter. The adapter plugs
into the trucks standard 7 pin connector.

The other side of the adapter has a 4 pin plug that the
trailer harness plugs into. Jeffrey

I have seen those. What I am trying to do is just use the 7 wire connector in a 4 wire to 4 wire connection. My initial problem is the 4 wire flat connectors never seem to last for me, so I want to use the stronger 7 wire style.

I ran into something like that recently. It seems the 7 prong RV type plug uses a different color code then the others.
George

I got the color code straightened out. It seems to be in the running light circuit. No running small lights or license plate light.

Some time ago I combined and edited/corrected this handy dandy sheet for trailer wiring color codes and positions in all common plugs, as viewed from both front and back of truck and or the trailer connection.

Print it out, laminate it, and keep it with your wiring supplies and tools.

Grigg

ps
It does not have separate picture for flat 4, but they come molded with colored wires. The colors/functions are same as the automotive 6 and 7 wire plugs (not all same as semi truck 7 wire)

Thanks

I am somewhat confused.
What I think you want is that the truck has a 7 pin connector. You want a mating 7 pin connector on the trailer. You only want/need to use 4 of the 7 to power the trailer. There is no 4 pin connector or 4 pin to 4 pin connector involved.

If this is what you want.
You simply use a 12V ice pick tester to see what each of the 7 truck pins operate, find the 4 functions you want, and wire 4 of the 7 trailer pins accordingly, with 3 not wired. Forget colors.
You will obviously have to apply brakes, turn signals and running lights on the truck while finding the 4 functions you want. That may take two people.

Be sure you know how ground is accomplished on truck and on trailer. Some are thru the ball, so be sure trailer is attached to truck ball and ball is making good contact. If the truck connector has it's ground on a pin, be sure that pin is carried thru to however the trailer lights are grounded. Most trailers ground the bulb sockets to the trailer frame, which passes ground thru the ball on truck. So don't mix apples and oranges regarding ground methods. Check to see how each trailer light is grounded. You may need a 5th ground wire. Use the tester to follow power all the way to bulb/socket if bulb won't light. Be sure bulb is not burnt out....or a fuse somewhere.

Typical trailer light function has a single filament for brake and turn, to signal a turn it interrupts the left or right brake light on the trailer. (running light is another filament for that only)
Your truck might not be wired in this way, you may have a stand alone brake light, and a stand alone turn signal filament? If so and without the right turn signal unit then your trailer wiring gets confusing.

A Signal Stat 900 turn signal switch is in my opinion the best aftermarket option, choose the 7 wire version and not the 4 wire. With the 7 wire it's real easy to power a trailer light plug properly. You can also have separate turn only bulbs on the truck if desired.
http://www.truck-lite.com/webapp/wc...;productId=47726&urlRequestType=Base
Not this
http://www.truck-lite.com/webapp/wc...e=Base&langId=-1&catalogId=10002

I suggest using the standard color code and positions for the standard trailer plug of your choice.
It's real frustrating having to rewire your trailer or truck to work with someone else's truck or trailer because you have something non standard.

Grigg, this a 1990 truck, so modern for me. I will use your info in the very near future to square away my 52.

What I am trying to do is use a 7 pin connector on both the truck and trailer to connect 4 wires on the truck to 4 wires on the trailer. I am doing this because I always manage to break the 4 wire flat connectors about the time it gets below zero. I have used the standard pattern of what function goes where on the connectors and taken the different color wires between 4 and 7 wire into consideration as well. So I am sure a 4 wire function is on the pin as a 7 wire function would be. I have the white wire pin on each side of the connections grounded to the frames of both the truck and trailer. I wanted both truck and trailer to have grounds as well as just the ball to hitch connection. I made sure the function pins are aligned on both connectors, by plugging them together and then sliding the housings off the wire connections so I can see both sides of the connection.

I will check the connections again, but the grounding comment may be the issue. The original trailer running lights grounded through the mounting screws and had just a power line going to the light. I replaced several of these with a two wire fixture and grounded to the trailer frame.

I can get brake and turns to work when the lights are off, but when I turn them on the trailer running lights don't work and both lights flash when I use the right turn signal. I am going to relook this again today or tomorrow, had to walk away for mental health reasons.

For the late model truck please disregard the turn signal switch stuff, I thought the question was related to antique trucks.

Sounds like you have issues on the trailer lights and or wires to them.

There is no difference in color code and function for 4 wire flat connector vs. 7 pin connector (as used on autos and pickups).
Yellow, brown, green, and white, all same functions for each type of plug.

As said,
1. Wiring messed up
2. Ground problem
3. Does not have dual filament bulbs
4. All of the above