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jp4bigblue

help with wiring harness and plug for trailer lights

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Ok, so my truck was a repo and the wiring harness and trailer plug are missing. I see where they cut the wires but it also looks like they had something rigged up here like some lights or something. There is a group of 5 wires grouped together in black wire protector. There is a red wire that looks like it goes back to the battery. Two other black wires.I have not bought the harness or plug yet. I want to be able to run the lights on trailer and charge the battery on the trailer while towing. Any help or advice would be appreciated.Thanks,Jason

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There should be possibly 2 wires from the front... one from a brake controler (not included but the harness plug in for it is above the ebrake mech.) The other would be a battery to the trailer. Some trailer harnesses include a ground & some do not.

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I stumbled across this, while looking for something totally different...

Subject: Re: 7-Pin Connector Wiring My 97 Ram did not have the factory trailer package. I wired the 7-blade connector myself, and soldered all connections before taping and sealing with black RTV. My truck had the front part of the harness and the connectors in the fuse box under the hood [power distribution center, PDC]. The 4 blade connector under the dash was there too. Of these 4 wires, the red/tan is "hot", tan/white is the brake sensor, black is ground, and blue is for electric brakes. At C128, 129 behind the front inner wheelhouse, attached to the bottom front of the cab behind the tire, you will find that the harness going from there to the rear of the truck is missing two wires that are needed for the trailer connector at the rear bumper. These wires are for the trailer running lights (black/orange) and trailer brakes (light blue). I ran 10 gauge wires to the rear for these functions, as I prefer heavier wire than OEM anyway. OEM used to be 14 gauge in 1995 and later they upgraded to 12 gauge. By tapping into the cab end of the connectors, you can access the power leads that you need from the front harness which has these functions even in non-trailer-towing trucks. At the rear end, I tapped into the brown/pink lead for right turn, and dark green/red for left turn. Violet/black is for backup lamps. From the PDC connection for the 120 amp fuse, I ran 8 gauge for the B+ (battery positive lead) that is used to charge the trailer battery, and another 8 gauge for a ground from the battery terminal. This setup with 8 gauge wires allows charging the trailer battery "on the road" much quicker than the stock 12 gauge wires would. In summary, you now have 7 wires: right turn, left turn, backup, 10 ga. running lights, 8 ga. B+, 8 ga. ground, and 10 ga. trailer brakes. This arrangement is heavier duty than stock, and was worth the effort for me. I also used a DrawTite "Ultra Frame" hitch rated at 750 lb tongue weight and 7500 lb trailer weight in weight carrying mode, vs. stock 500/5000. The Draw Tite uses 9/16" bolts, four per side, vs. stock metric which are about 7/16" and three per side. Joe

Subject: trailer towing wiring -- Beware all those who crawl under and lay out wiring for their trailers in their RAMs... The CC trailer harness is available as an aftermarket part and SHOULD be used as it contains a relay for the clearance lights of the towed vehicle that does not go through the headlight switch. The switch CAN NOT take the current flowing to feed some 6 or more clearance lights and it will "fry" the switch. I have seen it several times! The trailer tow option includes the relay tripped from the headlight switch, and the aftermarket CC harness is installed exactly the same way. (retail some $90 +/-) The harness also includes a fuse for circuits A6 the battery feed, and L76 the feed from the relay to the trailer parking lights, license light, and side/front/rear marker lights. Don't tow without the relay or a similar setup or I promise you you will buy yourself a new headlight switch eventually!! Bob Subject: Re: trailer towing wiring One thing CC didn't put in the trailer tow package which ,IMHO, is a necessity is a relay on the charge line. If your batteries are in a discharged state on the trailer and you hook up they could pull down the battery in your truck preventing you from starting your tow vehicle. I put in a heavy duty relay in the charge line and used the cigar lighter as a feed to energize the relay when the ignition switch is in the on position. A relay in the back up light circuit would also be useful for replacing those pathetic stock back up lights on the truck. This relay would also solve burning up your back up light switch when additional lights are added to your trailer for backing up.

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