Troubleshooting Problem With Demco Diode Kit On 2013 Jeep Wrangler

Updated 03/13/2026 | Published 03/08/2026

Products Featured in This Question

Demco 4-Diode Universal Tail Light Wiring Kit for Towed Vehicles - 7-Way to 6-Way Adapter Cord

(98)

$227.30

Roadmaster Hy-Power Diode - (Qty 1)

(351)

$20.53

Question:

I had a Demco wiring harness and plug installed on my 2013 Jeep wrangler to be flat towed. All has worked good until today. First all my Jeep lights work and when I connected the Jeep to the motor home both left and right signal lights and running lights will not work. Both plugs have checked good with a light meter. I cleaned the ground on the frame. I have a left turn blinking light before and after on the diode but no power to or from the right signal light diode. The left signal light does not work although power is traveling through its diode. Is this a bad diode?

asked by: Michael C

Expert Reply:

Hello Michael, thanks for reaching out, and good job on the troubleshooting so far. This sounds like either a bad diode, or a break in the tow wiring between the or 6-way plug and the diode on that side. I’d check continuity on the right turn wire from the front plug back to the diode and inspect for a pinch or rub spot along the wire. Diodes can fail, but it's not common. Based on what you’re describing, I’d suspect wiring before replacing parts.

Check that and let me know your findings. I'm happy to help troubleshoot further if needed.

If you do end up needing one new diode you can replace it with the Roadmaster Hy-Power Diode # RM-790.

expert reply by: Jesse M

John C.

3/12/2026

I installed the base plate, diode tail light wiring, Demco stay and play brake system and Tow bar in my 2024 Mini Cooper with no issues. It all works perfectly. I would suspect a bad wiring connection especially if the plastic quick connectors were used. I always solder and shrink wrap wiring on trailers and did the same with my Mini Cooper Toad.

Jesse M.

3/13/2026

@JohnC Hey John, thanks for sharing! Yes those plastic quick connectors aren't the most reliable. Great tip about soldering and heat shrinking all the connections too.

Ray

3/12/2026

voltage after diode would say open from there to or including light.,, or failed ground. Continuity test mentioned is a start if no voltage coming into diode. Often problems at wiring to plug loose or shorted. Incandescent bulbs or LED ? Incandescent often need cleaned for contact. Slight corrosion can give intermittent trouble.

Jesse M.

3/13/2026

@Ray Thanks for the tips, Ray. That's super helpful!

Hugh

3/13/2026

Last year I installed Demco diode kit and wiring harness on a 2017 Mini Cooper without incident however a couple days later the Mini registered a current draw warning (interesting feature of the Mini). I literally went back through every connection and ground and in some cases re-installed new connectors but the current draw remained. In an effort to isolate the location I disconnected the leads on one side then the other. Turns out the draw was coming from the left side. Nothing make you crazier than trouble shooting after installing a new part because you assume that the new part can't be the problem. Well, to cut to the chase it was a bad diode. Contacted eTrailer and they very graciously sent me a new one. Problem solved and no other issues. Hope this helps.

Jesse M.

3/13/2026

@Hugh Hey Hugh, thanks for sharing! These are great troubleshooting tips, and I'm sure others in the same position will find this extremely helpful. Glad to hear you got it sorted out, and that we were able to get you a fresh diode. Nice work!