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Discussion Starter #1 (Edited)
How to install trailer light controller harness - '97 Grand Cherokee ZJ

Hello all,

Wiring your '94-'98 ZJ for trailer lights is easy, although the '94-'98 Grand Cherokee ZJ w/o factory tow pack needs an expensive harness. As far as I can tell this is because the brake and blinker lights are integrated into one bulb on the ZJ's and the stock wiring can not handle the extra amperage. For these reasons a harness is recommended. Anyway, once you get over the sticker shock of the part you will realize that the custom harness is real easy to install and ultimately worth the money.

I got mine for $50 special ordered via a trailer supplier in Ann Arbor, MI. They wanted almost another $50 for the install which I'm glad I did myself. Sidenote: Many online retailers seemed to have a generic picture for what was labeled as a '97 CG part and that did not give me enough confidence to give them my business...

I decided to write this because all the other instructions online seemed hazy and I couldn't find the info readily available when I was looking.

Here is the part that was ordered for me. It is a Tow Ready PART NUMBER: 118349 T-One Connector Easy DIY Trailer Wiring. http://www.towready.com/content/products.aspx?lvl=3&parentid=0&catID=1505&part=118349. Even this product has a generic image that is significantly different from what was inside, go figure.

You plug two pigtails from the harness in between stock wiring connectors, run a power line from the battery, run a ground wire, and connect a few wires with crimp things.





Here are all the included pieces organized neatly, it comes with the exact number of connectors you will need.



And a close up of the controller unit. It has some adhesive foam tape on the back so that you can securely mount it inside the rear electrical panel I mounted mine at the blue dotted line on the next image.



First things fist, lets take off all the panels that will be in the way. Move spare tire and check out the access panel behind it. Thats the stock wiring in my '97 ZJ w/o tow pack, thats the driver connector that you will connect into.



To get to the passenger connector we need to remove the four screws that hold the tailgate bottom sill (lip?) panel, then begin to work towards the passenger side so you can get behind the passenger panel.



In the picture above the dotted squares represent hidden panel clips like this.



So now you are ready to disconnect the factory connectors and reconnect them with the trailer light module pigtails in between. Here is a hint: The factory connectors slide easily on and off of their mounts.



So now you should have connected the shorter of the pigtails between the connector on the driver side and the pigtail with the long wires between the passenger connector. I chose to route the wire from the passenger pigtail underneath the carpet like so.



Now drill a small hole for the screw provided inside the access panel and attach the ground wire.



Now you have to connect power to the battery. The instructions recommend that you can run the extra wire provided along the frame rails underneath the car, I prefer to run my wires inside the car, your call. Luckily I already had a wire from the battery for my amplifier so I shortened the spare wire, added on the fuse holder and connected it to my amplifier wiring. I'm pretty sure this is OK as long as the existing wiring can handle the additional amperage, however you should make your own call.



Before you button everything up you should test everything, if it checks out ok you can re-attach all your panels and replace all the screws. Congrats. If you have comments or additional info post it below. Hope this helps a few members out.

-Matt
 

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You'll be fine connecting that to your wiring for your amp(s). That draws such a small amount of power that it's not going to cause any issues. Nice writeup, BTW.
 

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Thanks for this writeup. Just installed the hitch from the Mrs old 93 Limited to my 98 Laredo... and in searching saw hints of differing harness being used and recommended. Now i see i cannot transfer the 93's harness over..

EDIT: Just ordered this kit from e-trailer.com. $58 shipped.
 

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I'm not sure what you do for a living now, but if that doesn't work out, you could go work for the NFL outlining how a play went down drawling lines and arrows. LOL

Good write up!
 

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Discussion Starter #5
Tow carefully!

Was a product design and engineering student at the time, got a little carried away with the wacom tablet! It's really helpful for me when people outline exactly what to do, so just giving back. Also, rockauto.com has a trailer wiring harness for around $40, so that might be something to check out.

One word of caution: Grand Cherokees with the factory tow package have an auxiliary oil cooler which will help protect the differentials from damage. I've been towing for about a year (obviously without the aux cooler). I did one overweight long distance tow (700+ miles) and then a bunch of medium tows (furniture, lawn tractors, etc), all on hilly roads. Now my differential is toast. I don't know if towing was the direct cause but I'm sure it contributed to pre-mature wear. So take it easy when towing!!!!!!
 

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The external oil cooler is not for the diffs...
 

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The external oil cooler is not for the diffs...
I agree with this ^, but those little Dana axles are weak to begin with. I had to change our 96 Orvis due to mileage, it was whining like crazy with very little towing.

Now about this write-up.... Very helpful and well done. Thanks for that.
 
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