Trailer Lights Left Side Turn Signal and Brake Lights Not Working

Question

Question:

Both lights are on. When I hit the brake on my truck the left side doesnt light up. Right side does. Right turn signal works but left doesnt

asked by: Chris W

0

Expert Reply:

Your brake lights and turn signals for each side are on one circuit. The left side turn signal and brake light is generally the yellow wire going into your trailer connector. The first thing to do is check the fuses on your tow vehicle.

Next, inspect and test the connector at the rear of your tow vehicle with a circuit tester, like # PTW2993. If the problem is there then you need to clean it, if necessary, and if that doesn't fix it the problem is in your vehicle.

If everything checks out at the connector then the problem is with the trailer. You'll want to inspect the trailer's connector and clean it if necessary as well. Then you'll want to follow the wiring down the left side of the trailer looking for any damaged or pinched areas on the wire itself. If you find any you'll need to repair them and retest your lights. You will also want to check the ground wires for each light, making sure they're grounded to a clean, smooth surface.

I've attached a help article that may be useful to you. If you try these steps and still nothing works, let me know and we'll troubleshoot further.

expert reply by: Charles S

0

Paul M.

9/7/2020

When l turn on my right turn signal on my truck my left turn signal comes on on my trailer. What is wrong. Thanks

Reply

Jon G.

9/8/2020

Sounds like either your truck or your trailer is miswired. Check out the attached articles on 4-Way and 7-Way connectors to see what functions should be on which pins.

Helpful Links

faq-wiring-4-way.aspx

faq-wiring-7-way.aspx

Reply

Ricci G.

9/1/2021

@PaulM Hello, I have a 2009 Ford Expedition XLT with a standard factory tow package. The left, right and of course the brake light on my 7pin connector doesn’t work all of a sudden. I don’t have the owners manual so I would like to ask which of the fuse # should I check in the fusebox under the hood. Thank you!

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Victoria B.

9/9/2021

If it is just the stop and turn functions, you will want to check fuse location 45 in the power distribution box under the hood. If the trailer running lights are not working, then you'll also want to check location 28 in the same box. These fuse locations are based off what I could find in the online Ford owner's manual for your Expedition

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Mark

9/5/2020

2010 GMC Sierra right turn signal works neither brake light works left turn light does not work.

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Jon G.

9/8/2020

Have you take then troubleshooting steps that Charles mentions above yet? If not I'd start there, and be sure to check out the article he linked. If that doesn't help then let me know and I can help you troubleshoot further.

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Joe J.

7/8/2020

Left turn signal light and brake light on 2014 Silverado works but trailer lights don't. I checked the fuse for the trailer wiring #17 on truck it's fine. Checked the wiring on trailer and connector it's fine. I get no voltage but when I take the bulb out I do,now I have another trailer and same thing.

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Chris R.

7/10/2020

We at least know the issue is somewhere on the truck. Since taking the bulb out resolves the problem, I'm thinking there's a weak ground somewhere that's affecting voltage. Make sure the main harness ground is still securely attached.

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Joe J.

7/11/2020

@ChrisR Thanks actually it was the fuse, looking at it I could not see a break but testing with an ohm meter it was bad

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Adam

7/6/2020

The left turn and brake light for my trailer lights doesn’t work. I have a Honda Odyssey and I’ve checked the rear fuses and the plug for the wiring harness. There is power back to that point for the left turn signal. Could it be the wiring harness itself that plugs into the vehicle in the rear cargo area that needs to be replaced?

Reply

Chris R.

7/10/2020

It could certainly be the harness. Have you tested the actual connector at the bumper? See if you get power there on the left turn/brake pin. If you do, then the issue is actually on the trailer. You'll want to check the main ground wires (both on the trailer and Odyssey) to ensure they're still securely attached to a clean, bare metal surface. Let me know what you find and we'll go from there.

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Adam

7/10/2020

@ChrisR thanks! It was the converter in the ody that was faulty. I replaced it and all is working!

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Chris R.

7/14/2020

@Adam Fantastic!

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Joshua H.

7/3/2020

My 2011 Silverado 3500 diesel Might have an issue. The trailer Left brake light stays on and the signal won’t work if course. The right side is fine. Trailer is a 2013. Checked all the fuses and nothing is blown. Cleaned all the connections as well.

Reply

Chris R.

7/6/2020

Have you tested the 7-Way on your Silverado to try and rule out where the issue is? If not, start there- see if you get constant power on that left brake/turn signal pin. If not, then the issue is somewhere on the trailer side. You'll just want to inspect any wiring on that circuit that you can, looking for an exposed portion that may be touching metal (or a neighboring wire).

Reply

Chris B.

6/30/2020

Having a similar issue. Right side everything works fine, no left turn signal on shorelines trailer. Problem started with my 2017 f150, and now persost with 2019 ram. Boat shop hooked a battery up to trailer and lights worked fine. Hooked the ram up to a different trailer and still no left blinker. Checked fuse under hood. Fuse is fine.

Reply

Chris R.

7/6/2020

It's very interesting that the issue occurred with two different trucks (seemingly pointing to the trailer as the issue) but also occurs with the Ram when hooked up to a different trailer (seemingly pointing to the truck as the problem....). Sometimes there's an additional factory relay tied to the trailer turn/stop light circuit. I know you checked the main fuse but look through your owner's manual to see if there's a relay as well - if so, replace it to see if it resolves the issue.

Reply

Zayd

6/26/2020

I have a similar problem. I have a 2011 Tundra with factory tow package. I'm getting 12V at the right turn/brake terminal in my 7-pin connector but nothing at my left terminal. I can't locate a fuse specific to the left turn tow circuit (my truck's signals work fine). Any ideas on where to look? I'm hoping it's not a wire break somewhere.

Reply

Chris R.

6/30/2020

Check out the fuse located in the #44 position inside the fuse box under the hood. I believe this may be tied to the trailer turn/brake signals. If that fuse is okay then your best bet is honestly to take the truck up to a local Toyota dealer because it will be extremely difficult to troubleshoot factory wiring.

Reply

Bart L.

5/22/2020

the left hand turn signal on my 2018 chevy 2500 duramax will operate as normal but that same signal and brake light on my fifth wheel camper doesn't work. The spade in the pickup socket will light up but not blink. the right side spade will blink. any answers? maybe fuse or ?

Reply

Chris R.

5/25/2020

It definitely could be a blown fuse under the hood. Check the fuse in the #14 position inside the main box (the underside of the lid will show you where exact this is). This is the fuse on your Silverado that's connected to the trailer left turn/stop light circuit. Let me know what find and we can keep troubleshooting if needed.

Reply

Tony

8/15/2020

I have a 19 Ram 3500. When I plug a fifth wheel trailer into the plug in the bed of the truck the left side doesn’t work at all. When I plug it into the bumper it does @ChrisR

Reply

Jon G.

8/27/2020

@Tony If that's the case then check the socket in your truck bed for any dirt or debris and clean that out. The next step would be to test the actual wires to see if they carry those functions. If they do then replace the socket with # PK11893. If you don't get those functions then you're going to need to swap out the whole wiring kit # C56070.

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Answer 1

You will first want to check the fuses on your tow vehicle. Some vehicles could have fuses for operating the turn signals and brake lights of a towing package. You will want to check if they are installed and working properly. The next thing is to…

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Answer 2

Without knowing the year, make and model of the vehicle, I can't really provide any specifics but I can provide you some general things to check. The first thing you'll want to do is determine if the problem is in the vehicle or the trailer…

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Answer 3

Most trailer wiring problems are the result of a bad ground. What I would do is start with the connectors. Maker sure the connectors on both the trailer side and vehicle side are free of dirt and corrosion and that they are properly grounded. Next, I…

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Answer 4

It could be a tow package fuse on the vehicle. Use the owners manual to find the locations of fuses/relays related to the tow package wiring to check them and replace as needed. If the issue is not a fuse or relay then you can test the vehicle side…

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Answer 5

Based on the number you listed the light fixtures you need is the kit part #TLL160RK for both lights or just part #STL116RB for right hand or part #STL117RB for left hand.

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Answer 6

The tail lights you have on your trailer are the ONE LED Trailer Tail Lights part #STL0067RPG for the driver side and part #STL0066RBG for the passenger side. Unfortunately, Optronics does not offer a replacement lens for this particular light so…

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Answer 7

Based on the number you mentioned and other customers who have mentioned it the replacement side lens SHOULD be the part #AL17RB. I say should because the SAE number isn't a part number which means it's not always reliable to pick out…

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Answer 8

It sounds like you may have installed the connectors of your trailer wiring on the wrong sides of the vehicle, or your trailer is wired backwards. First thing you should do at this point is test the 4-way of the wiring harness with a circuit tester…

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Answer 9

First, disconnect the trailer from the tow vehicle so you can check the vehicle side connector. Using a circuit tester like part #PTW2993, test the functions of the connector; specifically check the right turn/brake, to make sure the signal is making…

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Answer 10

Unfortunately, we have not had a chance to install the Demco Hijacker Autoslide Locking Plate part #DM6025 yet. However, I have attached a photo of the product installed for you in addition to the instructions which list each step with a photo.…

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Answer 11

It is strange any time a turn signal works but the brake light on the same side doesn't. this is because the brake and turn signal lights are on the same wire/bulb. The usual culprit is a bad ground. Ground problems normally show up when there is…

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Answer 12

The most likely cause for the turn signals not to work when the running lights are on with your trailer is a bad or weak ground. It's very possible that a weak ground connection can be just strong enough to allow sufficient current for some…

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Trailer Lights Left Side Turn Signal and Brake Lights Not Working

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