Truck/Trailer wiring issue....Truck side.

[jsturkie]

Guys, I have an issue that popped up herea couple years ago. '03 Ram towing '95 Sea RayLaguna 18 CC. My truck has somehow lost the ability to power the right side brake light on my boat trailer. I have confirmed it with a multimeter. (Trailer) Green/Brown Channel has voltage and works. Yellow/Brown plug is not working (Truck side). Running lights work, ground pin is grounded. This is a factory MOPAR plug. I have checked all fuses. I tested for voltage all the way up to the fuse box under the hood tracing the circuit. . Thats really hard BTW with the looms and cable ties. I have power at the fuse. I just want to know if anyone has any ideas! I am towing a boat trailer and everything works but the right brake light. That side blinker dosent work as well but thats the same channel. To rule out some questions. All lights work on the truck, no issues at all. I'm positive its the truck and not the trailer because I jumped a 12v batt to the boat plug and tested all functions. Worked great. I'm a good troubleshooter but I'm at a loss on this one. Thanks for any help gentleman!!!! (Some back info...My wife mixed up the brake and gas at the landing and dipped the back of my truck in salt water! Salt water is where problems are born!)


Thanks,
Brandon

 

[EddiePetty]

Re: Truck/Trailer wiring issue....Truck side.

Brandon,
As you have traced the culprit lead from plug to fuse and report no power past the fuse; make up a long jumper, set your meter to 1K ohms and check the circuit for opens. I highly suspect a corroded connector towards the aft end of the truck...especially in either the plug or first connector forward of the plug.
As an after thought: Most MoPar rigs have both the flat-four and RV plugs. If yours is so equipped, have you checked both plugs? (The connection diagram is usually on the cover of the RV connector. )

 

[Scott Danforth]

Re: Truck/Trailer wiring issue....Truck side.

if you have an aftermarket wiring harness for the trailer wiring on the truck, in addition to corrosion the culprit may be the diode pack. I am on my 2nd trailer wiring harness on my 2000 Dodge.

 

[jzellers]

Re: Truck/Trailer wiring issue....Truck side.

Hey Brandon,

What you describe seems to be the same issue I just repaired on mine. I have an '03 Ram 3500 and my left brake/turn went out on the trailer harness. It was a broken relay on the circuit board under the fuses. Some have had issues with their boards burning due to the 15A fuses being stronger than the board's circuit , but mine was simply something inside one of the three (all the same part #'s) relays.

If you turn on your right turn signal, go to the fuse box and listen. On mine it sounded different than a normal relay would sound and it was obvious there was an issue with it. I ordered replacement relays from relaycenter.com, P/N AZ988-1AT-12DSEC3R and replaced all three.

I also installed an isolator (I used a Modulite Ultra) so that there would never be more than a few milliamps of draw on the truck's trailer wiring. This requires running a 25A circuit to the rear of the truck, but I already had a 60A 8GA wire to power my electric winch. The isolator was probably overkill, but then again, my relay went bad powering only LED trailer lights with no shorts in the system. I've also heard of guys installing the isolator modules by tapping into the actual truck light wiring and bypassing the truck's trailer circuits altogether.

If you find that a relay is bad and you want to tackle the repair, someone did a great job writing it up. I'm not sure we can post links to other forums here but you can do a google search on "Dodge RAM PDC Repair" and it will pop up right near the top. This is a two hour job or less if you're comfortable with soldering on circuit boards. Otherwise it's pretty expensive to replace the board.

Hope this helps...

Joe

 

[jsturkie]

Re: Truck/Trailer wiring issue....Truck side.

Guys, Wonderful job on the replys. I am in debt to you all. Petty, I have both 4 plug and bumper connectors but the bumper outlet only plus into the 4 pin. I dont even use it. I don't think that would be an issue. I think Jzellers has it nailed. If it was a bad connection, I think I would have sniffed it out by now but who knows. I have been waiting on a day under 90 degress out to pin this down. I'm going to use all of your help. That makes me think, my '91 S-10 pulled trailer wiring off of the rear lights, why must we pull it from the relay box these days?? Good luck guys!!! Thanks a million and Zellers, sounds like you have one hell of a truck. I'll reply soon.