Community Forums

Hamshog · 04-21-2025, 11:43 AM

Flat towing our Ram. I installed a 4 wire diode harness on the truck. Lights don't work when plugged into the motorhome. I've double checked all wiring and verified power thru the cable from my to truck. Help!

Howard

FIRE UP · 04-22-2025, 12:30 AM

Quote:

Originally Posted by Hamshog

Flat towing our Ram. I installed a 4 wire diode harness on the truck. Lights don't work when plugged into the motorhome. I've double checked all wiring and verified power thru the cable from my to truck. Help!

Howard

Well Howard,
I just finished the total setup of getting ready to tow our new-to-us 2021 Ram 1500 Laramie Crew Cab 4x4 Ecodiesel. I've been setting up vehicles/trucks to be towed for years and years and when it came time to set up ours, for the life of me, I was having a hard time finding the correct tow-harness for our particular truck. Then a member on here linked the proper one and I looked it up and ordered it. It was definitely a plug and play.

While we've not towed it just yet, I have checked the lights out by feeding the umbilical with 12V power to each pin and a ground to make sure all the different lighting applications worked. And they do just fine.

As for yours, well, if you have verified you have all the correct signals migrating through the umbilical from the motorhome to the truck, you now have to make sure those signals are getting all the way back to the wiring harness you installed. Once you have verified you have ALL those correct signals (i.e. left turn/brake, right turn/brake and tail/marker) to that point, you need to make darn sure your GROUND from the coach is also making it all the way back to where you did all that wiring. They (all the mechanics on the planet) say that a very large majority of electrical issues in the 12V systems of any vehicle are related to a BAD GROUND.

So, do make sure your ground(s) are all intact. And also, recheck the part number of the wiring harness you purchased and make darn good and sure it applies to YOUR year and model of Ram. As I stated, I had to look for the applicable harness for ours. Apparently there's different ones for different Rams. Hope this may help some. Please get back with your results.
Scott

FIRE UP · 04-27-2025, 11:09 PM

Well,
No report back yet, oh well.
Scott

Hamshog · 04-29-2025, 03:42 AM

Scott, thanks for responding. Did you use the Curt system? You didn't mention it. Let me know once you hook up...

Howard

FIRE UP · 04-29-2025, 10:50 AM

Hey Howard,
Thanks for getting back here. Well, to answer your question, the lighting adapter harness and the 6 pin plug up front were/are both Curt. The harness part number (at least for our particular year and model truck) is: #58975 and the Curt 6 pin plug (very commonly used) for the front of the toad is: Curt 58090.

It all works outstandingly well. And just because I could, I built a test box for testing not only all that work recently done on the Ram but also for testing ANY trailer or toad lighting/wiring now and in the future. Cool little tool/toy. This way, I don't have to have the motorhome close to the truck or our Jeep or our boat to test the lights on any occasion.
Scott

Dodge Guy · 05-05-2025, 09:50 AM

I made my own harness with a diode kit. Has worked great. If you wired the end correctly then the problem is somewhere in the harness.

FIRE UP · 05-05-2025, 10:47 AM

Quote:

Originally Posted by Dodge Guy

I made my own harness with a diode kit. Has worked great. If you wired the end correctly then the problem is somewhere in the harness.

Yep,
I did the same exact thing for decades. Only the diodes I used were from Amazon and were about $2 each. I'd simply cut the incoming wire to each tail light, insert and solder in a diode, then between there and the tail light plug, I'd "T" into it with the incoming line from the coach. It worked slick for decades. But with todays wiring and CANBUS stuff, I figure I'd just let someone else's research and development take care of all the blown fuses and body control module blow-ups and when they had a final harness, I'd buy one. Tough to beat a plug and play harness.
Scott