Trouble Shooting Trailer Wiring?

[ALMike]

I've got a 16 ft bumber pull with breaks on one axle, and a set of rear brake / turn / running lights. It's got a 7 pin RV blade connector to my truck. I've got one 3 strand wire that runs to the electric brakes, and a two strand wire running to each of the rear brake / running / turn light units.
Nothing works though - I've got continuity between the ground plug and brake wire on the RV blade, but nothing else on the connector has continuity.
What should I look at / fix to clear this up? I assume that the rear lights are grounded to the frame, since they just have a two strand wire running to them, the frame is getting some corrosion on it.
Any tips on how I can use a multi meter to identify the potential source of my problem(s)?

 

[Diamondpilot]

Check the tow vehicle. If its a newer Ford/GM it has separate fuses and circuits for the trailer plug/vehicle lights.


Check all your grounds.

Chris

 

[SnowRidge]

First thing to check, besides the fuses, is continuity between the connector's ground pin and the frame of the trailer. Same for the tow vehicle.

 

[Scooby074]

Trailer wiring..my nemisis

If nothing on the trailer is working, and you have power on the trailer side of the plug, then you likely have grounding issues.

I usually dont mess around with troubleshooting trailers, especially it it uses a frame ground. Its almost easier to rewire with new wire and run ground to all the lights then to spend hours chasing corrosion, loose connections and somebody elses work. If its your trailer, a rewire with soldered, heat shrinked connections and ground run to all lights, will save you headaches in the future.

My 2cents

 

[2manyrocks]

The leads on multimeters won't reach from the connector at the front of the trailer to the taillights, for example. I get a long piece of wire I know is good and attach an alligator clip to each end. Then I can check using the multimeter. Sometimes helps to use the voltage part of the multimeter and make a drawing of which prongs on your vehicle are supposed to do what. Then start checking to see if the trailer is wired the same way.

Usual suspects are a ground wire that doesn't have good connection because of rust and bulb grounds that also have corrosion preventing a good connection. Then of course, there's always the problem that someone has wired the trailer to match their truck connectors in a way that doesn't match my vehicle.

Often, the trailer wiring is so bad that I just start over with new wiring. Cheaper than a ticket and much, much cheaper than an accident.

 

[weldingisfun]

Check the tow vehicle. If its a newer Ford/GM it has separate fuses and circuits for the trailer plug/vehicle lights.


Check all your grounds.

Chris

Dodge uses a different wiring pattern from the one used in the trailer wire coupling. Took mine to an RV maintenance shop and the fellow switched two wires in the trailer cable coupling, problem solved. Sorry, can't tell you wihich two wires he switched.

 

[Diamondpilot]

It is usually the positive wire that charges the trailer brake battery and the trailer brake actuating wire. Its the center pin and I believe the #2 pin on a 7 pin connector. Not sure at this time but have all the diagrams at the shop. To make things more interesting I have seen GM products with 7 pin connectors and no brake controller lock up trailer brakes as soon as its plugged in. Again, just 2 wires switched.

Chris

 

[mlauk]

I would start out by disassembling the connector on the trailer end and see which wires go to what on the truck end (usually labeled on the truck end connector) they should be:
yellow wire - going to the left rear for stop and left turn
green wire - going to the right rear for stop and right turn
brown wire - going to both rear lights for running lights and also to the side markers
white wire - grounded to the trailer and for brakes
blue wire - power for brakes

 

[Soundguy]

I just got done completely rewiring my 16' trailer after a whole host of issues.

I cleaned up every ground with new connectors and never sieze greast.. I added a seperate ground cable fromt he frame that hooks to my trailer via quick connect.

I also had to replace the plug on my truck and trailer.. plug on the trailer got corrosion onthe back of it, and the plug on the truck had the blades spread and made bad contact.

If your trailer is a 6-pin setup and you use a 7to6 adapter.. some need a wire swappe dinternally for the brakes.

Also.. the brakes onthe trailer are really only 1 wire .. or 2 if you count ground.. it's just 'hot' to the electromagnet.

Your brake controller only really needs power and ground and brake power to the brakes to work using the panic button, plus the 4th wire fromt he brake switch to work automatically..

post back some more info.


soundguy

I've got a 16 ft bumber pull with breaks on one axle, and a set of rear brake / turn / running lights. It's got a 7 pin RV blade connector to my truck. I've got one 3 strand wire that runs to the electric brakes, and a two strand wire running to each of the rear brake / running / turn light units.
Nothing works though - I've got continuity between the ground plug and brake wire on the RV blade, but nothing else on the connector has continuity.
What should I look at / fix to clear this up? I assume that the rear lights are grounded to the frame, since they just have a two strand wire running to them, the frame is getting some corrosion on it.
Any tips on how I can use a multi meter to identify the potential source of my problem(s)?

 

[J_J]

If you will take the plug apart and identify the wires, write down your findings on paper. First locate the ground pin, and see if it is grounded to the trailer. After that, use 12v battery and test lead and check each of the other pins. If you have help, they can tell you if the lights are working. If no help. use a mirror set up in back of the trailer and do some logical troubleshooting. some tinfoil and tape will make a reflector. Write all your findings on paper. Those 7 pin plugs are not all wired the same. When you are finished and everything is working, make a schematic of the trailers wiring diagram.