Jeep Wrangler Light Wiring

[buzzbill]

We've been towing our Wrangler behind our motorhome as a flat tow for over a year now without a problem. We haven't moved it in a while, though, and since we are prepping for a big trip I wanted to check to make sure the lights work. Well, this time no luck.

I took out my trusty multimeter and ensured that I had voltage through the 7-pin connector on the back of the motorhome. So, it isn't the motorhome. I ensured I had voltage through the 7 to 4-pin converter as well. Then I tested the brown wire and ground coming out of the 4-pin connector going to the Jeep lights. Again, I had voltage.

I am not an electrical engineer, so I am assuming that I must have a short somewhere between the 4-pin and the lights. Is there a fuse in the Jeep that the wiring is usually linked to? Am I making a false assumption that voltage coming through the connectors means that the connectors are not at fault?

The lights on the Jeep work fine independent of the motorhome.

Any insights would be appreciated.
Thanks!
Bill

[Ljwt330]

Originally Posted by buzzbill

We've been towing our Wrangler behind our motorhome as a flat tow for over a year now without a problem. We haven't moved it in a while, though, and since we are prepping for a big trip I wanted to check to make sure the lights work. Well, this time no luck.

I took out my trusty multimeter and ensured that I had voltage through the 7-pin connector on the back of the motorhome. So, it isn't the motorhome. I ensured I had voltage through the 7 to 4-pin converter as well. Then I tested the brown wire and ground coming out of the 4-pin connector going to the Jeep lights. Again, I had voltage.

I am not an electrical engineer, so I am assuming that I must have a short somewhere between the 4-pin and the lights. Is there a fuse in the Jeep that the wiring is usually linked to? Am I making a false assumption that voltage coming through the connectors means that the connectors are not at fault?

The lights on the Jeep work fine independent of the motorhome.

Any insights would be appreciated.
Thanks!
Bill

Forgive me for not knowing the relationship between wire color and circuit, but I'll ask a few questions.


First, what, exactly, fails to work on the Jeep? We need to know that to help troubleshoot. Brown usually connects to the tail lights, but we need to know if that is the fault in your wiring.


Second, you tested the brown wire in the cord plug from the MH, but what about the other wires from the MH cord--the ones for the lights. brake/turn signals? Again, we need to know which circuits fail in the Jeep. If brown is for running lights, is that the only malfunction?


In my Wrangler, the wiring harness connections can be exposed after removing the left rear tail light assembly. You might check there to see if anything is amiss. Use your meter and check for power at the connectors behind the tail light assembly. Also, check to see if the harness of the Jeep is securely grounded--either close to the socket in front, or near the tail light.

[buzzbill]

Thanks for the quick reply!

To answer your questions, neither the brake, turn signals, nor running lights work on the Jeep when attached to the motorhome.

I suspected that the 4-pin was the problem, so I only tested the brown wire with the ground since my understanding was the the brown wire works the running lights and those are the easiest for me to check with the motorhome. I just checked the other two wires and both have voltage on the Jeep side of the 4 pin.

Thanks!!

[Ljwt330]

Originally Posted by buzzbill

Thanks for the quick reply!

To answer your questions, neither the brake, turn signals, nor running lights work on the Jeep when attached to the motorhome.

I suspected that the 4-pin was the problem, so I only tested the brown wire with the ground since my understanding was the the brown wire works the running lights and those are the easiest for me to check with the motorhome. I just checked the other two wires and both have voltage on the Jeep side of the 4 pin.

Thanks!!

Okay, if I understand you correctly there is voltage to all circuits at the end of the cord, but when plugged into the Jeep socket, you have no running lights, brake lights or turn lights. Is that right?


If so, my next step would be to look just behind the socket attached to the Jeep and see if there is any obvious problem, and follow the wires as far as you can easily see. If all looks good, remove the left rear tail light and expose the connections from the tow wiring. Test to see if there is voltage at each of the connectors from the 4-pin wiring to the Jeep's wiring. If no voltage, there is a break somewhere between the socket in the front and the connections at the rear. If there is voltage, there is a problem with the way the 4-pin wires were spliced into the Jeep's circuits.


Since your lights had worked in the past, I suspect something simple like the wires have somehow pulled out of the socket in the Jeep or the socket itself went "bad." Very easy to disassemble and/or replace if necessary.


Note, the above is how my Wrangler is wired which, I believe, is typical.

[Ljwt330]

One additional thought. Check the ground wire from the Jeep socket. If that wire is not grounded to the Jeep frame, power from the lighting wires will not "flow."

[buzzbill]

Thanks for all the ideas! I thought the ground was the issue and completely hooked up, but no joy. Checked the lights as suggested and nothing looks wrong. I am getting 13.4 V through the multimeter. My wiring setup has a diode. Could that have failed?

[buzzbill]

Thanks to your advice, I was able to track down the problem and correct it. It was, in fact, a flawed ground connection. Really appreciate the help! Cheers!

[Ljwt330]

Originally Posted by buzzbill

Thanks to your advice, I was able to track down the problem and correct it. It was, in fact, a flawed ground connection. Really appreciate the help! Cheers!

Glad I could help, and thanks for reporting the solution so others may learn.

Happy and safe travels