Left turn signal not working

[Overclocked]

In 2018 I purchased a 2018 Jayco jayflight 267 bhws & I purchased a new 2018 F150 xlt v6 3.5l EcoBoost to pull it. Another camper notified me in 2019 or 2020 that my left camper turn signal was not working. I've tried each year:

1. Check truck fuses
2. Clean truck contacts both at connector & behind by disconnecting the wiring harness.
3. Check camper and truck ground.
4. Check camper fuses
5. Clean 7 pin camper connector
6. I disassembled the turn signal to Check connections & reconnected. I wish I took a picture of wire colors. I believe it was green, like right turn signal.
7. I purchased a 7 pin & 4 pin connection tester and tested the truck and the truck side is fine & tested good.
8. Every now & then my truck would say left turn trailer light fault. Not all the time. Note, see question 2 below.

Today I connected a battery negative to - on camper wire harness & positive to left turn signal. I got a weak dim left light. The same as hooking up the truck.

Then I removed the power box cover to check wires. I found:
1. The yellow with red wire from emergency break was connected to nothing?
Q1. Where does this connect to?

2. The left turn signal from 7 pin �� wiring harness was cut & not connected to anything (yellow wire)? All other wires were connected to trailer matched pair.
Q2. It appears that they did not run the left & right turn signal in parallel green & yellow wire. They must have connected in series? If this is the case, how does the left turn signal work? Do I connect the yellow wire to one of the existing connectors or do I have to run a new wire to the left turn signal? But how does that work with stop lamp, backup & flashers?

Reference 2 pictures 1 for yellow wire from emergency break & 2nd external box that houses the connections between wire harness & trailer.

[ggilbert]

Yellow wire is reverse light. I have the same exact camper. Left break light and left turn are the same wire(Red).

My light was bad.
This is the replacement i bought
You get both lights.

Command Electronics 9.5" Oval Red... https://www.amazon.com/dp/B07F7H2Y49...p_mob_ap_share

[Overclocked]

The confusing thing for me was that the truck side left turn signal uses the yellow wire at 3 o'clock to it appears based on the trailer side diagram you provided connect to the red wire on the trailer harness. I thought yellow mated with yellow & then why was my yellow wire in camper junction box not connected to anything? But it appears the yellow on camper side is reverse lights. See pics. And Thanks. I had a 3rd pic showing the wire harness inside the frame with the yellow wire at the 3 o'clock position verifying the truck diagram. But it didn't upload.

I almost purchased the lamps last year but I had a friend stop over with a brand new Dodge limited. We connected it & it worked? So I was baffled. And purchased the truck wire harness tester

[Overclocked]

I am buying them now

[RedHorse1]

So it works with your friends truck but not yours. Sounds like the connector. I’d use a VOM and check the left turn to ground terminals in the TV connector. If that’s good, pull the bulb and check the volts at the turn lamp. Could be the 7 pin TV connector is not connecting with the TT plug.

[Overclocked]

Just for nomenclature: TV connector is trailer side & TT is truck side?

Q1. When I go to use a volt ohm meter and check the TV connector (trailer side) by connecting the VOM black (-) to the (+/ground) of the trailer connector & the positive to the left turn signal...what am I looking for? (ohms or continuity check to make sure the circuit is not broken)? I was trying to find a youtube video on this to see what I was looking for?

Today I directly connected (with alligator clips) a 12V marine battery negative terminal to the (-) on camper wire harness (TV connector 11 O'clock position) & positive to left turn signal. I got a weak dim left light. Now looking at your wiring diagram I connected the negative of the battery to the power of the connector. I will have to redo tomorrow morning before church. The result of a very dim Left turn signal is the same as hooking up the truck.
So directly connecting a 12V marine battery so far has not shown to increase brightness of the flashing left turn signal. Just the right most vertical row of 2 LED's is fairly bright. The rest are dim. So when you have your running light on, they overpower the dim flashing turn signal lights that they never show the left turn signal flash.

Q2. Tomorrow when I pull the bulb and check the volts at the turn lamp,
I touch the neg of the Volt meter to white wire of light (ground) & (+) to red wire (left turn lamp). I should see > 12V correct? If I get >12V then that would indicate a bad light/bulb. If it measures <12V then I have a big problem?

Note, today when picking up my camper from storage, I asked the guy if he had another trailer that I could hook up my truck to to test left turn signal. He had a 16' flat bed trailer with 7 way plug & we tested. The left turn signal worked fine.

Onto the last note above, last year I thought the same thing that the connectors weren't contacting. So I purchased a dielectric grease & applied. Then I spread apart the truck-side connector prongs to increase contact (by making the "hooks" wider. This is when I thought I first saw the the left turn work for 10 seconds. But never again, even 1 minute later.

After church tomorrow I will have my friend come over with his new truck & see if the turn signal works this year. If it does, then I am baffled again. In that I purchased a TT -tester & all indications is that the truck connections all work; Then I tried it on another trailer & it worked; & I cleaned & increased contactor contact. If it doesn't, then the light is bad.

It still bugs me why the yellow wire in the junction box is not connected to anything. I was thinking this was the answer? If you have a chance, could you remove your cover & tell me if your yellow wire from the TV connector going to this box is connected to anything? or is it the lone wire in the box like mine, picture 2 in original tread.

Thanks again

[SmokerBill]

The hot wire going to the left tail light might be shorted to ground somewhere, maybe a screw cut through the insulation. And if that's the case it could be an intermittent problem.

Looking at the picture, you can place a jumper between the black/12vdc and the red/left turn and brake, to get power to the light. Do that, then remove the tail light fixture from the trailer and gently move/pull on the wire and see if it changes the state of the problem.

Maybe the hot wire or ground wire is poorly connected to the tail light and needs to be resoldered. Or maybe the problem is somewhere else in the wire between the plug and the tail light.

Don't worry about the yellow wire. It's for backup lights.

Did you remove the wire nuts pictured in your first post to make sure all the connections there were good? Specifically, the two red wires connected with the yellow wire nut. I think that's the wiring connection for the left light.

With no power going to the left light, use your meter to check for continuity between the outer part of the socket and the trailer frame (bumper, etc,). If the meter reads close to zero ohms, the socket is getting a good ground. If not, there's a poor ground to the left light which would cause your problem.

[Overclocked]

Thanks SmokerBill. When you mentioned jumper black & red, you mean in the external junction box. Jumper there then connect power?

[Overclocked]

I tightened wire nuts. Light was not as bright as rt signal,
But brighter than before. I then jumpered red to black. . And it was dimmer than before jumpering. Then I removed the jumper & really tightened the red and black wire wing nuts. Now the light is bright. I will hook up truck now. It works. Thanks to everyone for your ideas and helping me and others improve troubleshooting skils.

[JFlightRisk]

I think he's referring to this. Looking at his diagram of the trailer plug, (the trailer battery will supply power for testing without having to connect to the truck) jumper between the black at 11:00 (12 volt power terminal), and the red at 3:00 (left turn and brake terminal). This will light up the left tail light like the brake light (no flashing).

By your first post, you've already determined the light is dim.

"Today I connected a battery negative to - on camper wire harness & positive to left turn signal. I got a weak dim left light. The same as hooking up the truck."

Question, are the tail lights LED or do they use a bulb, like an 1157 (marked on the brass base)? The bulb style lamps are notoriously unreliable from cheap bulb sockets, and iffy ground connections. That's why I upgraded ours to an LED insert. A picture of your tail light would help.

Next, looking at your pictures of the junction box, I'm suspect of the single wire in the top photo that's sticking out of the loom. It doesn't look that yellow in the picture to me. Was it like that when you bought the TT?

In the bottom picture, the tail light connections should be the ones with the yellow caps. One left, and one right. I had the same style box on our TT, and when I was upgrading to a Pollok screw stud terminal box, I found corrosion under the ground connection cap. The metal boxes aren't water resistant, and they're right in the water spray when driving in the rain. Did you by any chance take all the terminal caps off one at a time to check all the connections?

Sorry to barrage all the questions, but if the tail light worked ok before, and not now, I suspect a connection issue. If it has always been dim, you'll have to eliminate all the possible causes. Let us know what you find out.

[JFlightRisk]

Sounds positive. You probably found the problem. (You posted that as I was thinking of possibilities to expound on).

For future reference, this is the junction box I upgraded to. You only need 7 terminals, but I opted for the 10 terminal box in case I wanted to add something later on.

www.etrailer.com/Accessories-and-Parts/Pollak/PK52248.html

[Overclocked]

Mine Are all LED lights, oval like the 1st reply mentioned with link to Amazon. However, you get 2 for the
price of 1. The 1st picture is yellow with some red color for the emergency break. Both this and the yellow wire in junction box were loose when purchased in 2018. The wing nut connections were original also. So I may have not had left turn lights for 4 yrs till someone mentioned it to me and every 20 miles the F150 said left turn trailer light fault. So the F150 diagnostics on the truck were right on, however, I could trust nothing until I found the problem . It wasn't until SmokerBill said to jumper red & black that I took the caps off and redid them.

I use electrical tape to cover junction box openings & seams. Does well.

I can't remember if the left tail turn signal ever worked. I park it and drive it and my wife never said anything. Then when a camper or driver pointed out on the hwy in 2020/2021 then I started to do all the troubleshooting above.

Thanks

[Overclocked]

Light from etrailer 1 Light. Amazon gives you both left , right & license plate

[Overclocked]

In my opinion, I believe the black wire was not contacting in the wire nut. It looked flat & not twisted. There were 2 larger diameter wires and 1 smaller one with it that contacted well.

[ggilbert]

Originally Posted by Overclocked

In my opinion, I believe the black wire was not contacting in the wire nut. It looked flat & not twisted. There were 2 larger diameter wires and 1 smaller one with it that contacted well.

When I replaced my pig tail because i jack knife and cut mine. Some of the wire nuts just fell off. I put tape on mine after I replaced the pig tail. It will take 30 min to remove all the black tape.

[garywilson]

In your original post you said you checked all of the fuses.

Does that include both fuses for left side?

I think there is one for the truck and another (in the truck fuse block) for the left trailer.

[Overclocked]

All fuses were fine. There were 3 in the engine compartment. But with the lights off, I could only faintly see the left light flash. When the running lights were on, they over powered the flashing lights.

I believe that black wire will not only fix my left turn signal, but It should also fix my breaks which never worked since day 1. My gain was always 10.0. I took off 2 tires & hubs and cleaned & adjusted breaks. I can't wait on my next trip in June to test out the breaks, set the gain to 3-4 & finally have a turn signal that works. That means from the factory that black wire caused a lot of unknown problems. Quality and inspections need to improve. I found 7 defects, 3 which I fixed, 3 they fixed & 1 I had to have a Lippert engineer travel here to inspect the frame and give his blessing on. Now my frame is warrented for life.

[Overclocked]

In the end, the wiring was loose white & black. However, I believe the original 7-way plug chord was either defective or damaged before purchasing. When I moved the chord to the left side, the problem went away for the whole trip. When it bends to the right, I get the turn signal working until I move the trailer - then it still failed until it is switched to the left.

[Overclocked]

1. The 7-way plug wire was bad - I initially replaced the 7-way plug & cut the wires beyond the bend with Curts plug. But it was cheap & returned. I would never buy these because they are light & thin & water can get in. The clamp mechanism doesn't tighten well. It strips. Instead I bought a new plug, wire & junction box with round wire connectors.

2. The junction box wiring nuts were causing the wires to loosen. Thus new box
3. The light was faulty. After replacing the wire, plug & junction box the left turn signal worked. It was very bright all the time. However, after cycling thru all light functions it had a defect where the light would stop blinking for 3-4 blinks & then come on for 30 secs to 1 minute then off for 3-4 blinks. So I replaced it & ran the lights for 10 minutes and no problems.

[skids]

Lucky find!