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Unread 07-25-2008, 02:51 AM   #1
waterboarder
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Installing Mopar 7-pin trailer adapter and brake controller on the JK

This will be my master thread for this topic, and will include the install for the trailer brake controller (:

Remove the bumper
I guess you don't really need to do this - I didn't do it when I installed my third-party 6 pin adapter - but it was such a pain in the *** that I wished I had taken it off. This time, I already had the bumper off for other reasons, but had I not, I would have definitely taken it off for this operation.

Drill the hole in the bumper
Fortunately for me, the hole that I had previously drilled in my Mopar off-road bumper (maybe a year ago) for a 6-pin/4-pin adaptor (third-party) was basically big enough. There were two issues:

a). The Mopar adapter is round, but one side has a flat part that kind of sticks out. I was able to deal with this by using a BAF (big-assed file) to grind away the necessary part of the bumper. It didn't take too much effort at all, maybe 10 minutes of filing and the job was done.

b). The 4 mounting holes for the screws I had drilled for the previous adapter did not line up with the 4 mounting holes for the Mopar one. Big surprise. So, we used the welder to fill in the 4 previous holes and then grinded it flat. Then I drilled the new mounting holes where they needed to be. In the process of this, I lost some of the OEM paint (powder-coating?) on the bumper that I will have to replace with Rustoleum. I am applying the Rustoleum (flat black) now. It will take a few coats I'm sure, but I'm in no hurry. I'm trying to do this without primer since it is past midnight and I have no primer - but if it does not seem to "take" then I will get some in the morning and give it a go.

Also, I'm a big fan of stainless steel screws and such - so instead of using the lame mounting screws that Mopar provides, I went out and got 4 stainless hex button head screws that look very nice and should be rust-free. I'm looking forward to putting them back on.

Mount the trailer adapter
I'll be doing this once the Rustoleum phase is complete. Not much to it - insert the 4 mounting screws, tighten them down. It's a little more complicated for me since I use one of the screws as a grounding screw for my bumper-mounted reverse lights, but nothing to write about here (:

Run the wiring
One end goes to the adapter mounted in the bumper, one end goes to the left tail light, and the other end goes to the front of the vehicle. Seems to me that doing this before mounting the bumper is going to be a lot easier, so that's how I am going to do it. In the process of running the harness to the front, I'm going to run a secondary harness of accessory wires for various things too. All wires 14g:

a). (yellow) trigger/power to backup lights
b). (brown) trigger/power to backup camera
c). (green) trigger/power to 12v accessory outlet in cargo area (to install later)
d). (white) ground wire (general purpose)

So, that's the plan. I'll pick up on this when I make some progress (:

7_pin_kit_1.jpg   7_pin_kit_2.jpg   7_pin_kit_3.jpg   bumper_1.jpg   bumper_2.jpg  


Last edited by waterboarder; 08-02-2008 at 02:39 PM..
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Unread 07-25-2008, 03:20 AM   #2
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Another picture for this phase...
bumper_3.jpg  
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Unread 07-25-2008, 04:59 AM   #3
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I did my owne and went to the trailer sells shop by the house they made it up for me. They did a great job price was Great. But the why you are going it is probaly the Best.
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Unread 07-25-2008, 07:05 AM   #4
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Quote:
Originally Posted by texasdog View Post
... I lost some of the OEM paint (powder-coating?) on the bumper that I will have to replace with Rustoleum. I am applying the Rustoleum (flat black) now. It will take a few coats I'm sure, but I'm in no hurry. I'm trying to do this without primer since it is past midnight and I have no primer - but if it does not seem to "take" then I will get some in the morning and give it a go...
I have made modifications to my Mopar front bumper and found that the Rustoleum "Textured" black color matches the bumper coating almost perfectly. After it is dry you can very lightly go over it with a 3M scotchbrite pad to remove the sheen and you cannot tell where you painted.
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Unread 07-25-2008, 07:29 AM   #5
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Looks like your doing it right....I guess the snow finally melted enough for you to sit on the ground behind the jeep
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Unread 07-25-2008, 08:12 AM   #6
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plug

Nice detailed thread man.
FWIW, I mounted my plug tucked in behind the rear bumper and faced it downward. I learned my lesson in my wife's FJ. Right after this picture was taken I tore it off the rear bumper and had to rig it back up so I could get my trailer back home. 4 pin ones don't get smashed up too bad on the trail, 7 pins are a different story.

yeehaw.jpg
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Unread 07-25-2008, 02:12 PM   #7
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Quote:
Originally Posted by jdrogers View Post
I have made modifications to my Mopar front bumper and found that the Rustoleum "Textured" black color matches the bumper coating almost perfectly. After it is dry you can very lightly go over it with a 3M scotchbrite pad to remove the sheen and you cannot tell where you painted.
Well, I'm skeptical - but I'm going to give your magic paint a try. It's a big deal too, because I was ready to put it back together this morning (:

I went and got some black textured and just sprayed it on there. Now I have to wait for it to dry. We'll see how it goes (:

Quote:
FWIW, I mounted my plug tucked in behind the rear bumper and faced it downward. I learned my lesson in my wife's FJ. Right after this picture was taken I tore it off the rear bumper and had to rig it back up so I could get my trailer back home. 4 pin ones don't get smashed up too bad on the trail, 7 pins are a different story.
If I smash up my bumper that badly, I think I'll have other issues anyway (:

Quote:
Looks like your doing it right....I guess the snow finally melted enough for you to sit on the ground behind the jeep
Actually, I'm doing this operation in the garage (:
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Unread 07-25-2008, 06:05 PM   #8
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Well, you were right jd - that textured stuff does look a lot like the bumper! I didn't bother trying to sand it down though - I figure a black square there is fine. Maybe I'll go back and scuff it over a bit after it has a chance to dry thoroughly. It looks OK though - certainly better than having a second big *** trailer connector on my bumper - which is what I had originally planned to do (leave the one in place on the left side, and install the new one on the right side).

In the meantime - this part of things is done. Pictures attached (:
bumper_4.jpg   bumper_5.jpg   bumper_6.jpg  
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Unread 07-31-2008, 07:56 AM   #9
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T-Dog,
Where was the cheapest place you found to buy a 7 pin connector? I just ordered a trailer for my JK and it requires a 7 pin flat connector so I will be referencing this thread on a regular basis!! Great write up by the way!!
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Unread 07-31-2008, 01:18 PM   #10
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Quote:
Originally Posted by Brent_f70 View Post
T-Dog,
Where was the cheapest place you found to buy a 7 pin connector? I just ordered a trailer for my JK and it requires a 7 pin flat connector so I will be referencing this thread on a regular basis!! Great write up by the way!!
I just got mine from the dealer. Much to my amazement, they had one in stock! I paid $81 for it - but I think I saw it on-line for maybe $10 cheaper. All things considered, I figured the dealer was the better choice.

On your trailer - unless you need the stuff the extra pins provide you (brake, reverse lights, accessory hot wire), you could always use a 4-7 adapter with your trailer. You can get one of these for under $15 at Walmart or some place (assuming you already have the 4 pin set up).

Look for more news on my trailer wiring related stuff soon - very soon (:
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Unread 07-31-2008, 01:53 PM   #11
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Thanks T-dog,
I will need all the connections. I just ordered a chaser trailer from www.adventuretrailers.com with all the options to include lighting package, extra battery, electronic brakes etc....Got 2 kids and a wife who have fallen in love with jeepin!! So I see MANY weekend excursions in my future.

I will follow your thread and suggestion and stop by the Jeep dealer on the way home.

Thanks again
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Unread 07-31-2008, 03:27 PM   #12
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Quote:
Originally Posted by Brent_f70 View Post
Thanks T-dog,I will need all the connections. I just ordered a chaser trailer from www.adventuretrailers.com with all the options to include lighting package, extra battery, electronic brakes etc.
Wow!!! I'm jealous (: I'm just going to have a crappy home-built version of that trailer - one day - whenever I finish it.

With the load you dropped on that puppy, no sense in skimpy on anything else. Get the Mopar 7-pin - it's plug and play, and get yourself a Tekonsha P-3 Trailer Brake Controller. You'll need a 20A type 1 (auto-resetting) circuit breaker for the power line on that thing too. More to come (:
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Unread 08-02-2008, 02:46 PM   #13
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Well, I installed the Mopar 7-pin harness. It was an uneventful install and went well. I didn't quite follow their routing plan - I think mine has it more tucked up and secure and I also used up all of the zip ties they provided and got some more out of my stash and used them too. I probably used twice the number that they provided (:

On the engine end of things, I modified the white and red wires. I snipped off the terminal connectors and attached spade connectors, so I could hook them to my custom-built electrical panel (http://www.jeepforum.com/forum/f96/custom-build-jk-electrical-panel-589165/). The Mopar red wire has a 20A fuse holder and fuse on it. Not really necessary for me, since I'm attached it to a 40A relay with a 20A fuse in front of it - but rather than cut it off, I just left it there. I just bundled up the blue cable and tied it in place next to the battery for now - I will not run it into the cabin until I make up a little harness for the brake controller wires. When I do, I'll snip the Mopar blue cable significantly. The end of it will live in the engine bay and be connected to the harness I make, and THAT harness will run into the cabin.

To do:
a). Finish making secondary wire harness for rear power connections (doing the last bit of this right now)
b). Route this harness to the rear, hook it up.
c). Re-install rear bumper, finalize all connections back there
d). Make trailer controller harness
e). Install trailer controller harness
f). Make trailer controller install bracket
g). Install trailer controller install bracket and trailer controller.

Last edited by waterboarder; 08-02-2008 at 03:01 PM..
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Unread 08-02-2008, 11:13 PM   #14
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Those rotten BASTARDS!!!!!

I have just spent HOURS of useless work trying to find out why the trailer harness was not working. I thought I would share my lessons learned.

Everything was all connected up fine and I decided to put my Mopar rear bumper (which has been off for weeks) back on, finally. I connected the bumper reverse lights, fixed the "tweak" in the bumper from off-roading (see thread from a couple of weeks ago) and tightened that ***** on there. It's quite a workout getting those bolts on, and I was happy to think that perhaps this would be the last time ever I took that bumper off.

Then I decided to try the 7-pin connectors, make sure they all work properly. The only pins that work are:
left turn, left brake, reverse, ground, positive. Right side doesn't work at all and no tail lights. OK, fine. I take the left tail light back off and inspect my work. There were a couple of ways to connect the harness, I guess I did it wrong. I connected it the other way, did some testing and determined that all harness connectors work as designated, except no tail lights. Now, I'm thinking this is strange - why would turn signals and brake lights work, but no tail lights - esp. when the tail lights on the Jeep work just fine. OK - fine - I connect the stuff up another way and that isn't helping. At some point, I noticed that I had a harness connected to ITSELF, completely out of the electrical loop, and this configuration was working better than when I actually had it connected to something. WTF is going on?

At this point, several hours have gone by and I'm pretty pissed off. I decided to get on the web and see if I can find any install instructions WITH WORDS, not just pretty pictures where you have to guess what the hell they're doing. No luck. However, I did run across some posts where people were talking about ordering a 4 pin Mopar wiring harness. No help to me, I'm trying to install a 7-pin. Then it dawns on me. Duh. I have the factory tow package with a 4 pin connector. That must explain the extra connectors over in the tail light area. So, I go take a look. Sure enough, the 4 pin harness is the one I was connecting to itself - explaining why it didn't hurt me any. It also let me eliminate that stupid thing from what I was doing. So, I moved it out of the way - connected my stuff back up, and I'm back to everything working but no tail lights.

So, I'm still, what the hell? Why would everything work but tail lights? At this point, I'm thinking maybe the 7 pin connector itself is bad. So, I try to get that thing off the bumper, which is some work because you can't really reach back there and get on the stop nuts easily. I'm thinking I'll have to take the whole damned bumper off again. Furthermore, the wiring harness that connects to the back of this thing has one of those little red lock lever things on it, which is even harder to get to. I'm sweatin' and cursin' like a sailor, slowly making some progress - and FINALLY I get that ***** off, test it with the multi-meter, and find out that all the connectors are good. ****! I took it off for nothing. Then I decided that rather than try to put the thing back on with nuts in the back, I would drill out the holes, tap them with fine threads, and use some different fasteners (ones I bought for the trailer I'm building) to just attach from the front and be done with it. Big improvement, esp. if I ever have to take that bumper off again. Taping the holes and making this improvement was a nice little diversion, but didn't really solve the main problem I was having.

So, I'm out there with the multi-meter and the test light and trying everything under the sun, trying to figure out why the damn tail lights do not work, but everything else does. I'm also thinking that i spent $81 on this factory harness to make things EASY and this is clearly not the experience that I am having. So - I figure that the connector itself is good, there must be a problem with the wiring harness itself. I'm looking down in the little hole at my nice and neat ziptie job, not looking forward to taking it all out and apart and such, esp. since I had also zip tied in my secondary rear wiring harness for various accessories. But ****, I've got no choice.

So, I tear the thing out from the tail light to the bumper 7-pin connector and testing for continuity and everything else - and I'm eyeballing this "device" that is in-line. So, I open it up and find a relay in there. I think, why the hell is there a relay here? No matter - I figure the relay must be bad. Fine. I grab a known good relay, put it in there, and still no workie. ****! I can hear that relay click when I turn the headlights on too, so I know it is working in there. No idea why they are using a relay to power trailer tail lights, but oh well, fine - whatever. So, I'm in the middle of testing pins, trying to develop ideas and wife is back from being out, wants to eat dinner. ****. So, I stop what I'm doing, go eat dinner.

I'm in the middle of eating my Chinese food and thinking about all of this, and the big red wire that goes to the relay. Now, I know there is no big red wire that comes from the tail light area, so where is this wire coming from? Then I think, well, it must be the red wire that goes to the battery (duh), but that's the "trailer accessory" wire - why would the use it to power a relay that goes to tail lights? Then it hits me. Duh!! The trailer accessory wire is one I wired up to switch #4 on my panel, so I can turn whatever trailer accessory that is connected to it on or off from the driver's seat. Then my Eureka! moment occurs. I stop eating dinner, go out to the Jeep, connect everything back up, set up my test light with ground on the 7-pin ground connector and the tail lights pin on the 7-pin connector, and ask my wife to turn the Jeep on. Then I tell her, "turn on switch #4" - and sure enough, on comes to test light. Those rotten bastards!!!!!!!

Summary
Mopar 7-pin harness uses a relay for the "running lights" pin on the 7-pin connector. Relay gets its power from the "accessory" wire, which is also another pin on the connector. If you wire this wire (the red one) to a switch, then your trailer tail lights will only come on when the switch is in the on position, but all of the other trailer lights will still work even if it is in the off position.

So, the question then becomes, why did they do it this way? I dunno. Maybe they figure that if you're using the 7-pin connector, you're going to tow something with a metric ***-load of lights that will come on when you turn on your lights and the Jeep's tail light circuit can't handle that much load, so the use the relay to power it from the battery with a bigger wire. They didn't do the 4-pin harness this way. I know, because I have their 4-pin harness, and it is not done this way. If the 4-pin harness can power the trailer tail lights from the Jeep tail light circuit, it seems like the 7-pin one should be able to as well.

The next question then becomes, what do I do about it? I can:

a). Modify the Mopar harness to eliminate the relay, thus powering this pin from the Jeep's tail light circuit.

b). Modify my wiring, changing the 7-pin "hot" wire from a switched circuit to an always on circuit. This will allow the Mopar harness to work as its designers intended, but mean I can no longer turn on or off some particular trailer electrical accessory.

c). Modify the Mopar harness to power the relay from a fused (not switched) hot line that I ran to this area for some undefined future use. This lets me get what I want today, at the expense of future expandability.

I'm not sure what I'm going to do yet, but at least now I know what the problem is and how to solve it - without taking that damned bumper off again (:

Update
I implemented a relay bypass. Tail lights now work, and they are powered by the Jeep tail light circuit, just like the 4-pin connector works. It's how it would all work if I put a 4-pin connector on my trailer anyway, so I don't see a difference. If I run into any issues, then I'll have the tail light wire on the trailer hit a relay and then power the trailer's lights from the trailer's battery, and Jeep will not have to care about it. Also note, I modified the Mopar harness a bit, so that the trailer reverse lights will come on via the same switch that will turn on the Jeep's bumper reverse lights.

Additional Notes
In related news - I have completed and installed my custom 4-wire wiring harness from my battery area to the left rear tail light area. This gives me one wire for switched bumper reverse lights, one wire for a 12v outlet to be installed in the cargo area, one wire for a backup cam to be installed in the future and one wire for undefined future use (although now I may have a use for it, see above). I routed this harness along the same path that I used for the 7-pin harness. It's like a wiring super highway under there.

Also, now that I have tapped the mounting holes for the 7-pin connector unit, I can attach or unattach it from the bumper much more easily, which will assist if and when I need to take the bumper off again.

Last edited by waterboarder; 08-03-2008 at 06:23 PM..
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Unread 08-03-2008, 04:56 PM   #15
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I couldn't help but chuckle a little at your writeup. I've been in similar situations myself.

I think your rationale is dead on for why Mopar did what the did in the seven wire harness. My suggestion, since you bypassed it, is to use LED lights on the trailer you're building. You shouldn't have to worry about overloading anything that way for sure.

But I have to ask while I'm posting...how heavy is the trailer you're going to be pulling? What's the towing capacity of a JK? I know a SWB TJ was like 1500 (and later years 2000) and the Unlimited was like 3500. I suppose at 3500 that brakes would be a good idea behind a Jeep. Anyway, I'm sure you know what you're doing, I'm just curious...


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