Mystery problem

[MegaBob]

I have a 2006 dodge Ram with a 6.7 engine. I just bought a new to us travel trailer . I have the tow package on the truck. I'm using a prodigy brake controller with 7 pin connection the trailer is a 2022 forest river; no boundaries 19.8 trailer. Now here is the mystery, I hooked up the truck to the trailer but the left hand rear turn signal does not light up! Checked the big box of fusses with a test light. All fusees are good. Any suggestions.

 

[HarryS]

Are you sure the fuse connection is good? You are only checking the fuse itself.

 

[GTyankee]

If you have a friend with a Tow setup
have them back up to your trailer
see if it acts the same ways as your wiring

or buy or borrow a 7 pin tow wire tester

 

[2003F350]

There is a good chance you have a wiring issue or an issue in your fuse box.

Years back my FIL had a 2003 2500, 5.7, 4x4, quad cab short box. Bought the truck (used) to pull a fifth wheel, which it did okay but that 5.7 wanted to scream the hole time.

HOWEVER - our first trip out I followed him, and noticed that his left rear turn signal did not work. His brake light did but not his turn signal, though it worked fine on the truck. We confirmed the issue at the plug, all fuses looked okay, but there was an extra in-line fuse in an electrical tape wrapped harness that came out from under the fuse box (I have no pictures of this, it was a good 15 years ago). THIS fuse would show current when the left turn signal was on, but the fuse for the left turn signal in the fuse box did NOT.

At that point fixing it was beyond my skills at the time, so off to the dealer it went with the info we had. They kept it for a week until they discovered that it had essentially been re-wired to make the truck lights work, and there were two ways to fix it - put a whole new wiring harness in it, or put a Ford computer from a similar year in it.

The issue is that those year Rams had the turn signals using separate bulbs from the brake lights. This required the trailer harness (which uses the same wire for both lights) to be able to accept a signal from both of these separated circuits, and bypassing one on the truck means the trailer harness doesn't get the signal from it. Fords of those years, however, used the same bulb for turn signals and brake lights, so the electrical signal went through the same wire and fuse. By putting the Ford computer in it, the trailer harness would see proper signals, and the brake light and turn signal on the truck now used the same bulb.

I'm not 100% sure that this will solve your issue but it's definitely something to look into.

 

[rzr6-4]

Mine did pretty much the same thing. Good fuses, checked the wire all the way from the trailer plug up to the TIPM, turns out the TIPM was no longer sending power. I needed the lights the next day and I wasn't going to spend $300 on a TIPM just for a trailer light to work, so I ran a jumper wire from the truck turn signal to the trailer connecter wires. Someone on here has suggested that doing that can cause issues with back feeding to a relay or something (idk, I hate electronics) but mine has been working good for a few years now.

 

[2003F350]

Mine did pretty much the same thing. Good fuses, checked the wire all the way from the trailer plug up to the TIPM, turns out the TIPM was no longer sending power. I needed the lights the next day and I wasn't going to spend $300 on a TIPM just for a trailer light to work, so I ran a jumper wire from the truck turn signal to the trailer connecter wires. Someone on here has suggested that doing that can cause issues with back feeding to a relay or something (idk, I hate electronics) but mine has been working good for a few years now.

It can, but it doesn't always. It's something to be aware of, so it's good that you're aware of it.

 

[Tulecreeper]

Grab a circuit tester and check all the pins. It's the fastest way to see if you have power to all of them. Takes 2 minutes.

 

[2003F350]

Grab a circuit tester and check all the pins. It's the fastest way to see if you have power to all of them. Takes 2 minutes.

Normally I'd agree, but on those year trucks it may not tell you what's wrong. Sounds like a couple of us have experienced the problem before, the brake lights on the trailer work but not the turn signal, and it has to do with the computer systems, NOT the trailer wiring harness.

 

[Tulecreeper]

Normally I'd agree, but on those year trucks it may not tell you what's wrong. Sounds like a couple of us have experienced the problem before, the brake lights on the trailer work but not the turn signal, and it has to do with the computer systems, NOT the trailer wiring harness.

Understood, but the OP hasn't said what he has done other than check the fuses so circuit tester and bulb check would be my next elimination points.

 

[MegaBob]

Hello group. Here is the latest. Had my neighbor come help me figure out the problem. It came down the trailer plug in connector on the back of the truck. I went to several RV dealership's no luck. I went to Dodge dealer. They wanted $183.00 and it would take 3 days to get here! I called Loves truck stop; no luck. I then thought of Rock auto. Bingo; they have it in stock and with shipping it's only $72.00. Will be here by Wednesday.
Thank you all for your advice.

 

[GTyankee]

I may be wrong, but i thought that the the 7 pin connector could be taken apart & rewired

 

[2003F350]

I may be wrong, but i thought that the the 7 pin connector could be taken apart & rewired

It can, but the stock one has sealant in it to keep water out. Aftermarket ones are not, and if they aren't done properly will fail again in short order (my shop has replaced the plug on several of our trucks, several times, because the aftermarket ones keep corroding. The truck that we always send to the dealer has had no such issues, and the ONE time it was replaced, it was replaced with a factory one and hasn't had issues since.

 

[CaptOchs]

Since the trailer is only a few years old and the truck is 18, I'd focus on the truck. It could be a broken ground wire by the sounds of it. I would suggest getting a cheap 12v circuit tester (light) and tracking it down.

 

[WayneK]

Back in my day many lights had their own ground wire and if a light wasn’t working it was often because the ground had corroded or loosened.

 

[JW2 Innovations]

Back in my day many lights had their own ground wire and if a light wasn’t working it was often because the ground had corroded or loosened.

Agreed.

I see the OP is tracking on the source (truck plug) being the issue, but how many times is it what you are pulling? For me most often, so sharing below:

I chased a lighting issue on a couple lights on my boat trailer. Got it working, then stopped working, can drive you crazy!!

I finally read an article somewhere about home running the wiring to the lights into a junction box with a 7way harness coming out of it. I put it up on the tongue of the boat trailer and ran wiring directly to each light giving me the run around. Issue gone years ago! Yes it's more wiring/time/etc to get it done, but I haven't had to touch it even once since is worth it to me. Would work for any type of 7way connection for light/brake/turn lights/etc.

Amazon LINK to one of many offerings like this.

Hope this helps someone.

 

[GTyankee]

That type of Junction Box are carried by Mobile Home Movers

They also carry a Outdoor Extension Cord for those times that the Mobile Homes wiring is so messed up, that they just bypass it

They also carry a set of lights

 

[truck2569]

I have a 2006 dodge Ram with a 6.7 engine. I just bought a new to us travel trailer . I have the tow package on the truck. I'm using a prodigy brake controller with 7 pin connection the trailer is a 2022 forest river; no boundaries 19.8 trailer. Now here is the mystery, I hooked up the truck to the trailer but the left hand rear turn signal does not light up! Checked the big box of fusses with a test light. All fusees are good. Any suggestions.

Did you check the plug itself. it just snaps in and out. That is what I had to replace when it happened to me. The one on the truck.