Installing a ZCI Harness Kit # 119250KIT in a 2004 Dodge Ram 3500 with a Camper and Towing a VW

Question

Question:

This looks like it will fix my problem, the apparently notorious left side lack of power to the trailer turn and brake lights on my 2004 Dodge Ram 3500 diesel quad cab. This truck comes with the factory heavy duty tow package with both flat-4 pin and 7 pin connectors. Everything worked fine when the truck was new. So, some questions. I have to use both the 4 pin and 7 pin connectors concurrently. The 7 pin supplies charging and lights to my slide in camper, a relatively rare 1968 Avion. I use the 4 pin to hook up a pair of led tow lights to my tow behind vehicle, a 67 VW bug. Will the kits 20foot battery power lead reach, or can i just splice on more? Do I somehow disable my existing tow harness or tape the connectors up out of the way and ignore it? Or what do I do to add a new 7 pin output to your kit? Really, I need some of my existing 7 pin connections to the camper. I wonder if I can just jumper the turn and brake outputs I need for the camper from just before the 4 pin output of your kit to my existing 7 pin, severing the current wires and /or just splicing in? I should say that the truck lights work just fine. Both the 4 pin and 7 pin connectors test dead at the left turn and stop pins. And last but not least, I cannot dismount the camper to easily access the truck tail lights another story. So I can only hope to be able to reach and identify the proper wires as they enter the back of the lights from under the truck. Your BMW installation video makes it look so easy. BTW, the camper lights consist of two tail light assemblies and ten running lights, all incandescent. Thanks. Hope I havent scared you off.

asked by: Guy C

0

Expert Reply:

Thanks for all the information that you have provided and it is very helpful to know that you have already tested the pin locations on the vehicle connection and there were two pins that were not working properly.

My suggestion is to check your vehicle fuse box just to make sure that there is not a vehicle fuse that is causing an issue with the partial loss of function on the the vehicle connection of your 4-way and 7-way. You should be able to find the fuse location designated for towing lights in your engine compartment, but your owners manual will indicate the fuse box location and which individual fuse(s) are assigned to towing lights.

I also highly suggest testing the vehicle connection point of your factory 4-way and 7-way on your truck. To do this you will need to locate where the vehicle wiring connects to the factory installed 4-way and 7-way. This will be under the rear bumper of f your truck and should be a square connection port You can start at the vehicle 7-way and 4-way connection and trace the wires to find this square connection port. Unplug the port and test the wires to the plug. To test the functions of the factory installed tow-package wiring you will need to use a circuit tester, (sounds like you already have one) and verify that all the functions that connect to the vehicle connection point (the square connection point) at the rear of your truck work properly. If the vehicle wiring leading to the connection point functions properly you then you might consider using a part like the Tow Ready Custom Fit vehicle wiring harness # 20135 to establish a fully functioning 4-way and 7-way. This would be direct replacement for your current 4-way and 7-way vehicle plug.

If you test the vehicle wiring to the connection point and there is still not a functioning signal for the left side functions then there is a issue with the vehicle wiring to the trailer connection point. You can definitely use the ZCI Circuit Protected # 119250KIT to establish a new 4-pole connection point. The modulite that you referenced is rated appropriately for the lighting that you have in your camper and on your towed vehicle.

My research shows that your truck is approximately 19 feet long in total length so your concerns about the 20 foot length of 12 gauge wire might not be enough are correct. Considering the battery location(s) and routing the wire to the back of the vehicle you might need additional wiring. You can can splice in additional 12 gauge wire, like # 12-1-1, as needed just make sure that the connections are secure. When routing this wire make sure that you avoid moving parts and areas that generate lots of heat, like the suspension and the exhaust.

Since the lights on your truck are working properly and you do not have access to the back side of the taillights then you will want to connect to the existing truck taillight circuits to install the # 119250KIT that will establish a 4-pole connection point. Make sure that you use a circuit tester to identify the correct wires for splicing.

With this new 4-pole you could use the existing 7-way that serves the functions that you need for your slide in camper, or install the Hopkins adapter # 37185 to install a fully functional 4-way and 7-way to replace you existing connection. To get all the functions to work properly on this adapter you will plug in the 4-way to the modulite that you have already installed, then either identify the 12V power lead into your existing 7-way and connect the black wire on the Hopkins adapter to this wire. Or you can run a new 12 Volt wire from the battery of your vehicle installing an in-line 40 amp fuse # PK54540 and using some additional 10 gauge wire # 10-1-1 (sold by the foot).

I have included links to the parts listed above, a couple of helpful articles, and a video (that you might have already viewed) for your reference.