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Old 09-17-2016, 06:55 PM
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2008 GC trailer wiring issue

i just recently put on the Reese 44748 Class III-IV Custom-Fit Hitch and ran the Ready 118425 T-One Connector Assembly wiring harness. that got me a 4 pin wiring connection which when tested with one of the small plug in testers everything checks out. I just bought a small camper that has a 7 way plug so i bought a Reese 4 way flat to 7 way (7418411). the adapter is only hooked up to have the 4 way connect to it. the 2 brake controller wires and the hot wire on the adapter are not connected to anything yet. I havent had a chance to get a 7 way tester but when connected to my trailer im only getting 1 volt of power at the tail lights

is this a case where i need the jeep hooked to a starscan to turn on the towing settings to get the lights working correctly?

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Old 09-18-2016, 09:26 PM
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Re: 2008 GC trailer wiring issue

I dont think so. On my 2008 I just installed the curt hitch and the t-connector and I dont see how the computer would have anything to do with it as it just piggy backs off of the existing lights. When you plug in the camper do the lights on the jeep still work correctly?
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Old 09-19-2016, 04:51 AM
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Re: 2008 GC trailer wiring issue

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Originally Posted by carbuff View Post
I dont think so. On my 2008 I just installed the curt hitch and the t-connector and I dont see how the computer would have anything to do with it as it just piggy backs off of the existing lights. When you plug in the camper do the lights on the jeep still work correctly?

i am fairly certain with the trailer connected the jeep lights still function normally. let me report back tonight when i get a chance to test all functions.

could you open the fuse box up by the battery and take a picture? when i opened mine the 2 relays labeled "Left trailer tow stop/turn relay" and "Right trailer tow stop/turn relay" are not present. i am reading those are not included unless your jeep had a tow package from the factory

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Old 09-19-2016, 10:02 AM
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Re: 2008 GC trailer wiring issue

The factory tow package relays are used to protect the vehicle light fuse from blowing should a trailer lighting fault occur. The relay contact terminals are dead end without the factory wiring.

Are you sure the white wire on the 4 to 7 way adapter is fastened adequately to a chassis ground point? Disconnect the adapter 4 flat connection and measure the voltage between the ground and brown wire pins on the vehicle side. It should be battery voltage with the parking lights on. Reconnect the adapter and measure between the 7 way contacts at the 7 and 11 o'clock positions as you look at it with the cover raised. (7 is ground) The two voltage readings should be nearly identical.


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Old 09-19-2016, 10:17 AM
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Re: 2008 GC trailer wiring issue

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Originally Posted by clarklaflare View Post
The factory tow package relays are used to protect the vehicle light fuse from blowing should a trailer lighting fault occur. The relay contact terminals are dead end without the factory wiring.

Are you sure the white wire on the 4 to 7 way adapter is fastened adequately to a chassis ground point? Disconnect the adapter 4 flat connection and measure the voltage between the ground and brown wire pins on the vehicle side. It should be battery voltage with the parking lights on. Reconnect the adapter and measure between the 7 way contacts at the 7 and 11 o'clock positions as you look at it with the cover raised. (7 is ground) The two voltage readings should be nearly identical.


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So if the 4 way is reading 12+ volts but when the adapter is on the vehicle and the ground is good then the adapter is missed up?

just wanted to make sure im understanding your train of thought
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Old 09-19-2016, 10:18 AM
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Re: 2008 GC trailer wiring issue

Quote:
Originally Posted by crazylikeacharger View Post
i am fairly certain with the trailer connected the jeep lights still function normally. let me report back tonight when i get a chance to test all functions.

could you open the fuse box up by the battery and take a picture? when i opened mine the 2 relays labeled "Left trailer tow stop/turn relay" and "Right trailer tow stop/turn relay" are not present. i am reading those are not included unless your jeep had a tow package from the factory

Mine did not have the tow package from the factory either. Im not sure about the harness that you installed. The pic on amazon might not be of the actual harness. Is it the one that plugs into each tail light on either side and then runs down to the middle of the bumper to the flat plug? Or is it the one that just plugs right into the factory trailer light plug in the trucks harness. I think you only need to get the dealer scan if you use the factory plug harness. And if you mean two relays in the box under the hood next to the fog light relay, no, I dont have them either.
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Old 09-19-2016, 10:28 AM
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Re: 2008 GC trailer wiring issue

Quote:
Originally Posted by carbuff View Post
Mine did not have the tow package from the factory either. Im not sure about the harness that you installed. The pic on amazon might not be of the actual harness. Is it the one that plugs into each tail light on either side and then runs down to the middle of the bumper to the flat plug? Or is it the one that just plugs right into the factory trailer light plug in the trucks harness. I think you only need to get the dealer scan if you use the factory plug harness. And if you mean two relays in the box under the hood next to the fog light relay, no, I dont have them either.
the wiring harness i have required the trail light harness to be unplugged at the bulb then this went right there . its an inline connection. each end of the trailer wiring has sort of a T where one connection hooks to the input from up front and the other side hooks to the tail lamp.

I will have to check out the ground but i am fairly certain it is grounded properly and to a clean surface
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Old 09-19-2016, 11:02 AM
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Re: 2008 GC trailer wiring issue

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Originally Posted by crazylikeacharger View Post
So if the 4 way is reading 12+ volts but when the adapter is on the vehicle and the ground is good then the adapter is missed up?

just wanted to make sure im understanding your train of thought
If the reading on the disconnected 4 flat is 12V and the adapter is grounded properly, you should read 12V on the connected 7 way contacts between 7 and 11 o'clock. If not, either an adapter internal connection is bad (highly unlikely) or the brown wire connection is bad somehow. Keep in mind that the ground on the vehicle side of the 4 flat is not used by the 7 way adapter. It has to have it's own ground to handle the larger total current load of the lights, brakes, and auxillary power.
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Old 09-19-2016, 11:09 AM
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Re: 2008 GC trailer wiring issue

Quote:
Originally Posted by clarklaflare View Post
If the reading on the disconnected 4 flat is 12V and the adapter is grounded properly, you should read 12V on the connected 7 way contacts between 7 and 11 o'clock. If not, either an adapter internal connection is bad (highly unlikely) or the brown wire connection is bad somehow. Keep in mind that the ground on the vehicle side of the 4 flat is not used by the 7 way adapter. It has to have it's own ground to handle the larger total current load of the lights, brakes, and auxillary power.
the more i think about this the 7 way adapter ground might not be in the best location. i will check tonight and report my findings
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Old 09-19-2016, 11:18 AM
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Re: 2008 GC trailer wiring issue

would a faulty ground be to blame for the trailer lights going out when the headlights on the jeep are on and the brake is applied?
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Old 09-19-2016, 03:57 PM
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Re: 2008 GC trailer wiring issue

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Originally Posted by crazylikeacharger View Post
the more i think about this the 7 way adapter ground might not be in the best location. i will check tonight and report my findings
The best place, if convenient, would be an existing bolt that attaches something to the rear subframe. For instance: When I installed one of these adapters on my Grand Caravan, one of the bolts that attached the rear axle rebound bumper was within easy wire reach. Couldn't have been any easier. Just make sure everything is clean, and free of rust.
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Old 09-19-2016, 07:52 PM
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Re: 2008 GC trailer wiring issue

okay i found my problem. i got home and checked the 4 way and all the pins read the right voltage. before checking the 7 way adapter i took the ground and cleaned a spot on the frame and attached the adapter ground with a self tapping screw. tested all the voltages and everything checked out. so i went to the trailer tail lights i am replacing with new housings. its a 2 wire tail light housing with a third wire for ground. after hooking up the two wires and the ground i checked the lights. they were dim like before. i decided to run a jumper from the mail trailer ground to the jeep ground and the lights got nice and bright. so somewhere between my trailer ground point through the 7 way wiring to the jeep there is a corroded or loose connection
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