Adding a 7-Way Trailer Connector to a 2005 Dodge Ram with Factory 4-Way

Question:

I have a 2005 Dodge Ram 1500 Crew Cab 5.7L Hemi. The previous owner installed a 4-way to 7-way plug into the proper spot on the bumper. He connected the 4-way plug to the trucks 4-way but did not connect the rest of the wires. The white is ground. There is a Black and two Blue wires left over. One I assume is for the brake controller and the other is a secondary 12 V lead. Under the dash he installed a 3020-p harness to the Blue connector for the Brake Controller. Under the back of the vehicle I found a white/tan wire which I believe is the brake control wire will have to ohm it out to check. In the fuse block under the hood there is a 20 amp fuse marked Trailer Battery. My question is: Where do I find the wire associated with this fuse? The wiring diagram from Mitchell On Demand5 states: Red/Vio for the wire color. Wiring diagram comes to a split. One side says w/box Trailer Tow 7-way wiring. The other split says W/O Box Wires taped together. What is this Box? and if the wire is taped somewhere, Where?? Any help is greatly appreciated. Thanks.

asked by: David B

Expert Reply:

It sounds like the previous owner of your 2005 Dodge Ram did most of the hard work for you. My recommendation is to simplify things. We should start at the 7-Way with hardwiring the remaining wires. First, ground the white wire to the truck frame.

that should leave 3 wires to connect. One of them is for the 12 volt power circuit, one is for output to the trailer brakes, and one is for reverse lights or auxiliary power.

The wire that is attached to the 11 oclock position on the back of the 7-Way is going to be your 12 volt circuit. That wire needs to connect to the vehicle battery via a 40 amp circuit breaker, # PK54540. Use about 25 feet of # 10-1-1 wire to go from the connector to the circuit breaker and from the circuit breaker to the positive battery terminal.

A truck that does not have the tow package is not set up with the proper fuses and you need to use a circuit breaker. When routing the wire to the front of the truck avoid hot or moving parts that could damage the wire.

Next, the wire that is in the center position on the 7-Way is for reverse lights or auxiliary power. You can connect it to the reverse light wire on the truck if the trailer has reverse lights, or to use as another 12 volt circuit you would route it the same way as above and use a separate 40 amp circuit breaker.

The remaining wire will be for the electric trailer brakes. If you determine the white/tan wire you found does go to the brake controller, attach it to that, otherwise, you will need to run a length of wire for the connector to the blue wire in a connector that is located under the drivers side wheel well.

The box it may be referring to could be associated with the power distribution box and would most likely be located near it. It would carry the appropriate fuses/relays associated with the tow package wiring. I cannot verify this but if that box is not there (no tow package) then the wires may be there, hidden beneath or behind the power distribution box.

These wires are going to be difficult to locate and hardwiring everything like I have mentioned above would be a lot easier than trying to figure out the previous owners wiring. I have included some links to some FAQs that should help you.

expert reply by: Michael H

Robert M.

4/18/2020

I have a 2005 RAM 2500 Diesel with a factory 4-way. I would like to add a 7 way connector. Is the 4-way to 7 way converter reliable in the long term? Can I follow your instructions above to wire the rest?

Chris R.

4/20/2020

Yes, a 4-Way to 7-Way adapter like # 37185 is a great option and definitely reliable. Unlike other wiring adapters, this is something you can absolutely mount to your Ram permanently (especially since it still offers you a 4-Way). It'll plug in to the existing 4-Way on your truck and the additional black (12V), blue (brake output), and purple (reverse lights) can be run to make it fully active. Install videos and the written instructions are located on the product page.