Running wire from tow package dead

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wrenchinup

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Bozeman MT
Ram Year
1997
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Cummins 5.9
My 1997 trailer package brown running wire going to the plug-in is out. It comes out of the factory harness, goes through the bumper. I know that the trailer wires are all independent from the truck tail lights. I'm getting the wiring diagram tomorrow but meanwhile was wondering if anybody out there has fixed this same problem. I've already replaced the relay under the hood, and the 40 amp fuse, and tested the replacements. I didn't see any fuse on the side of the dash that would fit the description. Any suggestion would be much appreciated.
 

RVGuy

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2015
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If it were my personal truck and I was sure it wasn't the fuse or relay somewhere that went out I'd just run a new wire.
I'd run a constant powered wire with a fuse at the battery to the back of the truck to the N/O side of a relay, then have a wire from the other side of the N/O contact to the trailer plug. I'd then run a wire from the closest running light (probably the licence plate lights) to power the relay coil when the running lights are on, then the other side to the negative from the trailer plug or negative from the light. With electrical I just find a lot of times it's easier/faster to just run wires than try to diagnose weird problems. Then again I'm used to working against the clock at work where time is money.
 
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wrenchinup

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Thanks RVGuy, I was thinking about a new wire and you've got a great plan for it here. I can get the four wires to the new relay like you said, but instead of a new hot wire from the battery, I think I'd just T off the black (always hot) wire with a fuse for the normally off side of the relay. As long as anything I put on that black terminal was fused, I think it might be OK (?) not sure
 

RVGuy

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It should be fine as long as the wire is sized for it. If it's the charge line to the trailer I just don't like using it because it's already so undersized that the battery on the trailer barely sees any charge from it. Adding another circuit of loads to it (unless they're LED lights, in which case it's barely any load at all) just saps a bit more of that precious charge from the trailer battery.
 

El Huapo

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When I ran wire for the bigger trailer (7-pin) hookup, I ran some 14ga SO (heavy-duty service, oil-resistant) cord from a new ckt bkr under the hood so it would be durable and not have much inherent resistance to cause voltage loss. It has worked fine for years.
 
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wrenchinup

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Thanks guys, this is very useful. Was wondering what the black wire was for. don't have a trailer battery but It would be a hassle to T into it, and I might need a trailer battery for a winch or something some day. El Huapo, where did you get the new circuit breaker, just added one from the battery? SO sounds great too. Thanks again
 
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