See if this helps...  http://www.goldengait.com/resource/7way_wiring_diagram/

Trial and Error? I'd get a 12v battery and a couple extra long wire leads--ground to the negative side of the battery and red wire to the positive side, see what lights up.. Connect it to the correct wire for the 7 pin flat.

If it were me, I'd change the truck plug out to a 7 Round instead of the trailer's.

I agree, switch the plug as long as you are in the process of rewiring.

All the trucks are coming with the 7pin Round RV plug.  It's the standard and has been for the last 10 years on new trucks.  By switching out, you could tow that trailer with a friends truck and not need an adapter.

OK so explain what you had when you started again please. I reread the previous posts and I think it would be helpful to start from the beginning. Did the trailer have a 7 way RV (flat blade) connector? Did the truck have the original 7 way RV connector?

Paul

Have you tried a temporary ground from the trailer frame to the truck frame. I usually do this while trouble shooting any wiring problems. I take a vise-grip and clean a spot on the truck frame, clamp a cooper wire to the truck and do the same for the trailer. That eliminates 90% of the problems when determining what is wrong. The other thing I would ask is have you added anything to the trailer such as an awning, replaced any broken screws, added anything to the upper left side of the trailer?

Paul

If I recall correctly on the trailer side you have a red wire which is the battery feed to the trailer. Other standard wire colors are as follows:

Green: Right Turn/Brake Lights

Yellow: Left Turn/Brake Lights

Brown: Tail Lights

Blue: Trailer Brakes

White: Ground

Pull the trailer plug apart, run a jumper wire from the hot pin on the truck, this should be the one at the 1:00 o'clock position, disconnect the red wire from the trailer plug, then connect the jumper wire to the red wire. Check the interior trailer lights and see if they work. If they do then that wire should be connected to the mating pin at 1:00 o'clock on the trailer plug. Do this while you have your ground wire clamped to the frame of the truck and trailer. If the interior lights work use the same procedure for the black wire, connect it to the jumper wire and determine if that wire feeds the tail lights or exactly what it feeds. If the black wire feeds the trailer brakes you should hear a click when connecting the power because the magnets will grab the inside of the brake drum.

Paul

I think you will find the black wire is for the brakes.

Paul

Sounds to me that the running light pin on the trailer is in contact with the 12v hot on the truck.

Are the brakes locked up, too? Are the brake lights (not running light tails) lit up?  

I guess its a possibility, though unlikely. You can always move trailer wires around to match your truck. The Round 7 pin RV plug wiring locations is pretty universal. I think you said you already took a volt meter to check the truck, well, I'd check again and write down the outcome of each pin location. (i.e. left pin = left turn, right pin= right turn, etc.) Check this against the corresponding trailer wiring diagram and see if you notice a problem.

You could also find another trailer to hook the truck to and see if it has the same problem. Or if one of your friends has a truck with the same connector, hook it to your trailer and see if the problem still exists.

Good luck. I hate electrical gremlins.

ok so we are still having problems. We hooked another ram 2500 up to the trailer and every light worked perfectly which rules out the trailer or the trailer wiring. My dad replaced the plug on his truck with an OEM chrysler one and hooked it to the trailer and he has turn signals, but when he hits the brake all the lights on the trailer light up and he has no running lights. He also hooked his truck up to another trailer and it showed the same symptoms. The problem is in the truck somewhere.

??????????????????????  How about the wiring TO the plug????????????????????????

I don't recall if you stated what year your Dodge truck was but do a google search and see what you come up with. Some of the Dodge trucks had a design problem where the turn signals on the left side would flash when you moved the turn signal lever to indicate a right turn. I believe there was a TSB on this problem. And I don't remember if it was in the signal flasher, the turn signal switch, or the chassis computer.

Good Luck, Paul

Then take a test light and check the "truck" plug. Be sure each terminal is reading correctly....  7 way is about middle of the page....  http://www.horsetrailerworld.com/home/wiring.asp