1998 Dodge Ram Trailer Wiring Diagram
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Discussion Starter · #1 ·
Hi,
my 98 did not come with trailer wiring. The PO spliced a 7 prong plug using just the tail lights.
I want to do it correctly for a 7 prong. I see there is a 4 prong plug that connects to the tail lights via plugs and connects to a 7 prong plug. It appears then there is two wires (what gauge) that run the length of the truck and go to battery and trailer brake.
Is there a good article somewhere on "how to"?. I want to be able to pull a trailer with brakes. I've been looking but not finding-probably shows I'm somewhat electrically challenged.
Appreciate any references or input
thanks
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I see I'm not the only owner with a A DIESEL TRUCK WITHOUT THE FREAKING TOW PACKAGE SERIOUSLY WTF!!!!!
I was able to source a factory NOS kit that had a relay for the load, back up lights, charge wire and all other wiring you just have to add the trailer brake wire.
I found it off some overstock website for 35$
Very nice Mopar kit NOS made in 1996 for 1994-1995 trucks and cab chassis trucks
Read here
Ram Trailer Connector Wiring
They don't mention a kit for the 98's but I'm sure it's out there
By the way it's 95% plug and play. Just attach a ground, a positive connection to power the relay (saves your headlight switch) then wire in your trailer brake to the harness
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Discussion Starter · #3 ·
And to add to it, it's the 8800k truck-go figure wiring would not be included. I'm curious to get input from the 98 folks to ensure there's not something different
And everything I'm seening is 94-97-I'm not finding 98 thus far
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Discussion Starter · #4 ·
Still troubleshooting...
I THINK I can use a 4 way (#118329) plus run the extra wires for reverse, brake and ground. I've got the brake controller plugged into the factory plug under the dash. Isn't there a plug under the front somewhere that the brake controller plug runs to? I'm thinking I can run the blue wire to from the back bumper to that plug and the hot wire to the PDC? Also, do I need a 40 amp breaker in the hot wire between the rear and the PDC???
Help
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I'll take a look at my truck tomorrow when I'm in the shop, both the '97 and '02 and see what they have for trailer wiring. The '02 had factory tow package from my knowledge.
A 40 amp fuse seems a bit high, unless it is a "trailer tow" fuse like the newer trucks. Most older trucks had individual fuses for each separate circuit (running lights, right turn, left turn, etc...).
Edit: I stand corrected. After looking at the FSM for the '01-02 it appears a 40 amp "trailer tow" fuse is in use. Also, I noticed you wanted a reverse wire. Most trailers do not have reverse lights, so you can neglect this wire if you like. 
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The reverse light circuit is also used for trailers that have hyd brakes, like a lot of boat trailers. Reverse keeps the coupling from compressing while backing. They can be easily identified by the flat 5 pin plug, although some have 6 pin and 7 pin round plugs.
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Post a pic of the tail light pigtail and I'll see if it is the same as the 97 I have. If it is you should be able to use the factory 97 kit.
The kit I have had a relay which is very important
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Discussion Starter · #8 ·
So, still researching this...
I found the plugs by the driver front tire. It's my understanding that one of these is where the trailer brake and other relevant wires terminate. Can I use this Mopar number 82401265 and just plug it in and run to the wiring to the bumper? Or do I still need to run a wire to PDC?
It's interesting. Lots of info on 94-97, but dang little on 98+
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So, still researching this...
I found the plugs by the driver front tire. It's my understanding that one of these is where the trailer brake and other relevant wires terminate. Can I use this Mopar number 82401265 and just plug it in and run to the wiring to the bumper? Or do I still need to run a wire to PDC?
It's interesting. Lots of info on 94-97, but dang little on 98+
That harness i showed you does not include a trailer brake wire. You will have to add it yourself. Only thing it does it allows you to plug and a play with the lights. It does have the blue trailer charge wire though
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There may be a harness plug near the rear fender and frame that you can get a Dodge harness and 7 wire plug(or other brand) and just hook it up. There may also be a blue plug under the dash near the steering column that a trailer brake switch hooks up to with a pigtail, instructions with any switch. Look for both ahd see what you find. Don't do the 4 wire, you need the 7 for the standard trailers. Plugs are available with both 7 and 4 wire. Mounting brackets may need to ba attached or ground to fit plugs.
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Interesting enough, my 98 3500 wasn't optioned with the trailer tow package either. I lucked out one time when I was at the junk yard and got a factory harness that runs from the front tire all the way back to the hitch. It was 100% plug and play. It came off a gasser, but was the same year & reg cab configuration. Those two factors are what you need to get the right harness. It had molded bends in the wire and clipped to the inside of the frame. Only bad part is it runs between the fuel tank and frame, so you will need to loosen the thank. It utilizes all the factory relays. All of that stuff was present on my 98. Attached from my 98 FSM are three pages of how the 98's are configured for trailer tow. Try to find the factory harness, it will make your life a lot easier......
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Discussion Starter · #12 ·
I saw those pics in my FSM (I just dont read pics very well). Etrailer says to us the the 4 prong kit (having a 7 prong plug at the hitch) and run a wire for power and brake to the front. It says to splice the blue at the plug under dash (I was hoping to not have to splice) and run the other to the battery via a 40A breaker (again I was hoping to plug into the pdc)-will that work? I will be towing a gooseneck horse trailer with lots of lights so it needs to be done right. Also, I do have a short time frame to do this. Finding a 98 QC is not an easy task as you know (often 98 is a curse)
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Discussion Starter · #13 ·
Finally have it figured out. Does anyone jnow what gauge the blue (trailer brake) wire is? I'm guessing 12 G but would like someone to verify plese
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Finally have it figured out. Does anyone jnow what gauge the blue (trailer brake) wire is? I'm guessing 12 G but would like someone to verify plese
#12 will ne ok ......
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I forgot to update my previous post, although it's of no assistance. My '02 has a t-connector on the tail lights and two wires ran to the front...
12-14 gauge wire is plenty for the brakes.
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Discussion Starter · #16 ·
So, here is where I'm at (the saga continues)
The PO installed "T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector". It is connected to a 7 prong plug that has the 4 prong connector and four additional wires (power for trailer batteries, blue for trailer brake, wire for reverse, and ground). So I will run the three wires to the cab using 12 gauge wire. I'll add a 40A circuit breaker for power.
Questions:
-Do I need a circuit breaker for the blue wire as I'm splicing into the plug under the dash?
-I've also read that the clearance lights on the trailer will overload the 4 prong system and may cause issues with the headlight switch.
Thoughts
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So, here is where I'm at (the saga continues)
-Do I need a circuit breaker for the blue wire as I'm splicing into the plug under the dash?
You could use a circuit breaker, I know both the Tekonsha P2 and P3 controllers protect this circuit internally from shorts. A 20-amp breaker should be plenty.
-I've also read that the clearance lights on the trailer will overload the 4 prong system and may cause issues with the headlight switch.
If this is of concern, you can add a relay on the clearance light circuit. This is what I plan on doing when making a "trailer fuse box" for my truck in the future.
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If you have the blue plug under the dash for trailer brakes, it should have harness wires running back to at least the rear fender. There is also a pigtail you can get from Dodge or parts stores to hook the brake switch to the blue plug.
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The full harness only runs as far as the font tire on a 98.
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The full harness only runs as far as the font tire on a 98.
Learn something new everyday...
If you can locate the harness connections, I would buy ~20ft of 7-way wire, splice in at the front connections, and run it to the rear. Much easier than trying to locate a factory chassis harness.
Source: https://www.cumminsforum.com/threads/98-trailer-wiring-question.1978473/
Posted by: giantsblues.blogspot.com