Questions and Comments about this Article
Louis H.
I have a 2011 toyota tacoma with a new T-one harness installed. I have a new 4 pin trailer harness with led lights installed on a 5x8 tilt trailer. Problem is everything works properly with my lights turned off on the truck but with them turned on: seems like the trailer brake lights are on constantly, no turn signals or variance when the brake is applied.
Reply from Les D.
@LouisH these are classic signs of poor grounding or loose wires. I have attached an exhaustive article that will walk you through all of the possibilities. First I would check the white ground wire on the back of the trailer wiring harness. File the metal clean and shiny where it attaches. If you can connect your trailer to a different truck, this will be proof positive that the issue resides on the trailer side or truck side.
Helpful Links
faq-4-5-way-troubleshooting.aspx
Wendell S.
I have a 1999 Chevy Silverado I was hooking up a 7 pin connector I have a light green wire coming from my wine out of my truck with no place to hook it to in the 7-pin where does the light green wire hook up to you
Reply from Les D.
I have attached a link that illustrates trailer wiring and connector layouts. The green is usually the right side Stop/Turn signal wire. You can use a tester like # PTW2992 to check its function.
Helpful Links
faq-wiring.aspx
Matt
Ok so I have my wires run and ready to connect on my trailer. I am putting in new LED lights and ran a flat 4 wire connector. I know I need to run the brown wire to my black wire, but where do I run the ground wire from the light? The ground wire is only about 8 inches long. And grounds to the tongue. What do I do with the other wire on the light?
Reply from Les D.
@Matt The ground wire on your lights attaches to a grounded metal part of your trailer, typically within the 8 inches of wire that you have. Make sure you attach to a clear bare metal spot. Use a file to clean if necessary.
Mike S.
Good advice This has been very helpful Thanks
Heather V.
I have a 2011 F350 turbo diesel with a factory towing package. It has two 7-way plugs, one in the bed and one under the bumper. The trailer running/tail lights stopped working. When I checked the truck 7-way plug at the bumper, I had power at the pin but no trailer lights. Trailer service checked trailer said the lights all worked in the shop both with testing and connecting to another truck. The next thing the happened was the right trailer brake/turn light was dim, then it went out. I now only have the left brake/turn on the trailer. Please help me, I believe there are several fuses and at least two relays in the wiring harness. I am not sure where to start tracing this problem.
Reply from Les D.
@HeatherV Let's verify your trailer service peoples findings. I guess one quick thing to try is plugging the trailer 7-pin connector into the bed outlet and see if you get any different performance compared to the bumper outlet. If there is a difference it could be a defective plug or poorly wired. It would not hurt to try a different truck, if you can, to make sure we know that the problem is truly on the trailer side or truck side. Lights not working or working dimly frequently point to grounding problems. On the trailer, just beyond the 7-pin is a white wire that will be screwed to the trailer frame. Take that off, and file the ring connector, and also file to clean bare metal where it attaches to the trailer then reattach and test. Same thing behind the 7-pin on the truck, there will be a white wire there connected to the truck frame that needs to be filed and reconnected. Test again. If still no power at the truck 7-pin we need to first check the fuses and then trace the power wires back to the source checking any inline fuses we find. Your owners manual will tell you which fuses in the fuse block are for trailer lighting. I have attached a document showing trailer wiring and which pins do which lights. Remember, you will need to have truck lights on to check running lights on the trailer, and flashers on to test turn signals. A tester like the # PTW2993 will make testing pins and circuits easier. See the attached video that shows how to use it.
Helpful Links
faq-wiring.aspx
tv-review-performance-tool-hook-probe-circuit-tester-ptw2993.aspx
Aj P.
I got a older haulmark elite 2 race trailer. 7 pin plug. Hooked up everything. Bought new lights for it because I thought the old ones were bad because they didn't work. All the wires under the trailer seem fine. Has a battery for electric breaks. Do I need a new battery for the brake lights and running lights to work. No lights or anything work on this trailer
Reply from Les D.
The battery on your trailer could be for accessories inside your trailer like overhead lights, etc. A small battery on your trailer could also be for "breakway brakes" that only engage if your trailer comes loose from the tow vehicle while driving. The power for your electric axle brakes, running lights, brake lights and turn signals come from the tow vehicle. First determine if the problem is with your tow vehicle or the trailer. You will need a tester like the PTW2993 circuit tester. then consult the attached document for what to measure on each of the 7 pins on the connector. If you do not have power at the 7-pin then the problem is on the towing vehicle. Check the ground wire that is is connected to a clean bare metal place on the frame. Also file the ring connector to ensure a good connection. If that does not resolve your issue then you will need to trace the power wires to the power source checking any fuses you find along the way. Also check your owners manual for which fuses in the fuse block support the trailer lighting. If the problem is on the trailer side check for power at each of the lights. If you have power but no light, check the ground wire or the bulb. I suggest trying all of these options before installing any new lights.
Helpful Links
faq-wiring.aspx
Carlo N.
I have a 28ft toy hauler, I put new brakes on &now I have a problem no brakes.
Reply from Les D.
@CarloN It sounds like you forgot to reconnect the ground or power wires. Each electric brake has two wires. One wire for 12-volt brake power and one for ground. All 12 volt brake lines connect to each other and at the front connect to the 7-pin wiring on the braking line. All of the grounds connect to the grounded metal part of the trailer. The wires coming off the brakes have no polarity so you can use either for power or ground as long as all grounds come together and all power lines come together. I have attached a document on trailer wiring that has a good illustration of this. Let me know if this works for you.
Helpful Links
faq-wiring.aspx
Bill J.
I have a new to me, 1995 2-axle, 2-horse WW trailer. It has the standard 7-pin connector and electric brakes. All the lighting work, however, the breaks become engaged as soon as the vehicle key is turned on. I've connected the trailer to two different vehicles with the same result. Somehow the breaks are getting voltage to engage even when the break petal is not pushed. Now i can't pull the trailer because the break system is always "on". Any thoughts on what's happening?
Reply from Les D.
@BillJ I would start by testing the wires on the 7-pin connector on your tow vehicle. Use a # PTW2993 circuit tester. Most frequently when people have this issue we find that the electric brake line has been swapped with the 12-volt accessory line. The circuit tester will easily show you this. I attached a video that shows how to use this tester, and a document showing how trailer wiring at the 7-pin connector should be.
Helpful Links
faq-wiring.aspx
tv-review-performance-tool-hook-probe-circuit-tester-ptw2993.aspx
Mokp
I have a big Tex utility trailer and with a seven plug connector and whatever it drives it appears that the brakes are on I looked at the wiring underneath and somebody has connected the ground to the power for the brakes what the hell is this a standard configuration or what can I do about it
Reply from Les D.
I have attached a document that illustrates standard trailer wiring. It also includes a good illustration of the trailer break wiring. Electric trailer brakes each have two wires on them. One for ground and one for power. Brake wiring does not have any polarity, so either wire can be used for ground or 12-volt, as long as all 12 volt wires run to the brake wire on the trailer, and all the ground wires run to ground. Typically the ground wires attache to the trailer frame near the brakes, while all 12-volt wires are tied together and run to the 12-volt connection on the trailer. Finally, your 7-pin connectors have a blue wire for the trailer brakes. The also have a pin for 12-volt accessories. Make sure these have not inadvertently been swapped. If they were, the brakes would be on all the time.
Helpful Links
faq-wiring.aspx
Danny S.
Hello. , I have a typical 2008 6x14 enclosed trailer , all the lights work great when plugged into my 2011 Tahoe but only 1 brake light and 1 blinker works when plugged into my 2001 Silverado 1500. , using the same adapter to each vehicle. Are these vehicles wired differently ?
Reply from Victoria B.
@DannyS These vehicles would not be wired differently with factory wiring. Vehicle wiring is standard so that it will work with all kinds of trailers without the need for tons of different adapters. The colors used for wires on trailer wiring may vary, but trailer connectors are wired the same by function. I would use a circuit tester on your Silverado's trailer connector to make sure that all of the light functions are working correctly at the truck's connector. This will help you narrow down the issue. Since the trailer works correctly with your Tahoe, I am inclined to say that the issue is on the Silverado. It may be corrosion in the connector or one or more blown fuses.
Manny R.
I have a 2014 GMC Yukon, 7 pin factory plug. I bought a trailer wired for 7 pin with an electric hitch. The electric hitch does not work on my truck but works on the truck the previous owner had, I believe it was a Toyota. Can someone point me in the right direction?
Reply from Victoria B.
It is highly likely that the power wire on your Yukon need the final attachment made under the hood so that the 7-way actually has 12V power. I have linked a help article that talks about this issue and covers how to make the necessary connections in the "solutions" section.
Helpful Links
faq-tb-0007-2007-2009-gm-full-size-truck-brake-control.aspx
Darrell M.
I connected a new 7-way to my truck for my trailer and brakes however now when everything seems to work but my running lights stay on after everything is off the keys off and they do not turn off I can unplug the main plug the tail lights will go off but if I turn the lights back on the tail light stay on again. And I'm using all standard bulbs no LEDs
Reply from Victoria B.
I would check all of your grounds to make sure they are secured to bare, clean metal. Sometimes if a ground location has some corrosion or something like that it can cause a short and pull power though the connector. I would also check your trailer connectors to make sure they don't have any damage, corrosion, or bare wires touching that could be causing a short to draw power on the taillights even when the truck's lights are off. If everything seems to check out, a battery isolation solenoid may do the trick.
Reply from Darrell M.
@VictoriaB Thanks, It ended up being the new 7-way. Rare but they are not always the best money can buy, even when it's a Hopkins. Of course now my brakes on the trailer are locked up when I connect my trailer to the truck.
Matt W.
I have a travel trailer and a utility trailer and I am towing with a 2019 tundra. Both have a 7 way plug. Towing the travel trailer, everything is fine. Whenever I am towing my utility trailer it constantly shows the trailer comes disconnected. This is most annoying. I have traced it down to the trailer brake system, but was unable to figure out anything from there. I notice above it shows different wiring configs for RV and Utility. Could this be the issue? I have noticed it one other time when towing another utility trailer? Is there an adapter, that I can use to eleviate this issue?
Reply from Victoria B.
7-Way Traditional and 7-Way RV-Style connectors are wired in the same configuration but use different wire colors to indicate wire function. If your trailers are wired traditional vs rv-style, this should not be causing your "trailer disconnected" issue. Have you checked your utility trailer's connector for signs of wear and/or corrosion? Sometimes these issues are cause by a weak connection at the trailer connectors and as you drive down the road the connection comes and goes. I would also check the wire connections at the rear of the trailer plug (if accessable) to make sure the brake wire isn't working its way out of the connection point. If you find the connector is clean, let me know and we can try and troubleshoot further from there.
Wayne F.
I have a 2008 TAB trailer that has a 7 pin connector. When hooked up to a vehicle with 7 pins all lights work correctly. I have a 1994 Chevy pickup with 6 pin and a 2015 outback with a 4 pin. Using a 6 pin to 7 pin or a 4 pin to a 7 pin brake lights ok, left turn signal work ok. running lights ok. Right turn signal all lights are blinking on the trailer. What can I look for?
Reply from Victoria B.
My first instinct is to check the light grounds. When there is a ground issue, the trailer lights can behave oddly, in ways that don't make sense. I think maybe when you're connected to your tow vehicle with the 7-way, the lights are getting a sufficient ground possibly through the 7-way connector. I'm thinking the two adapters don't provide the same ground connection and are possibly causing this issue. I would check the ground at the right-side lights that are acting up, as well as the trailer's main ground.
Fidel B.
By screwing the connection box of my 7 pin wire under the clip of my fifth wheel m I crushed a wire and there was smoking, so I closed the master switch of the battery. The 7 pin cable was not connected after my pick up. My q question is it would be the wire of the brakes that I would have to pierce with the aim which would have caused a short circuit. Thank you for your good advice,
Reply from Jon G.
While our charts show what the typical wire colors are for trailer wiring, there isn't a law saying they have to be that color so you'll just need to test each wire to see what function it carries.
Jim N.
I have a 2019 GMC Seirra Denali and I bought a new car hauler. The problem is I bought it about 200 miles away and the left signal light dosen't work. Since it would cost more to haul it back than pay someone to repair it. I have checked all the connections I can find and checked the bulb all are fine. Any help will be appreciated.
Reply from Jon G.
Have you checked the fuses in your pickup? Attached is a link to our helpful article about troubleshooting wiring that you can check out.
Helpful Links
faq-4-5-way-troubleshooting.aspx
Al
What a great article very informative. I do have a question. I am switch my old rv tail lights to a led tail light. Upon looking at the wiring it has 4 wires coming out hooked to old light. New light has 3 wires from partsam light. I am going to systematically test each to find out what works what. But does any of those effect my trailer brakes, like if I hook them up wrong? Because I'm going to have to combine 2 of the wires together so they can connect to one of the three wires? Right help!
Reply from Jon G.
First just to clear the air, your trailer brakes are on a different circuit than your lights so you can rest easy there. When it comes to different amounts of wires what we normally see is that one of the lighting units uses the mounting hardware to ground while the other one used a wire. Testing your wires per function is the absolute best way to make sure you have everything hooked up correctly.
Plumberjohn
I have a 1973 slide-in truck camper. I'm trying to connect the electrical pigtail from my 2002 Chevrolet Silverado. The slide-in truck camper had a 6 Pin round (male), and the truck has a 7 Blade round (male). Is there an adapter or cable to make this possible? I'm not able to determine what pin does what on the slide-in truck camper. Any advice is greatly appreciated! Thanks!
Reply from Jon G.
You should be able to use something like part # 47549 for your application. With this adapter the middle pin is setup as the hot lead.
Clifford B.
I have a 2009 Ford F 150 with the 7round plug and a 4 flat wire plug I can use either one just bought a new set of magnetic lights with red and orange lens and already have the led lights mounted in the trailer only all lights work when head lights on truck are turned but no brake or turn signals I have a 7 pin to flat 4 round connector why is it that the lights work but not the brake or turn signals
Reply from Jon G.
Have you checked to see if you're getting a signal on those pins without the lights connected? It could be that you either need to replace some fuses in your truck or that you have a bad set of magnetic lights.
Gary S.
I have a Wells Cargo Auto Hauler trailer. Originally in the black box that houses all the connections (located on the front tongue) there was a diode in-line with one of the wires. My friend borrowed the trailer, and somehow burnt out (melted!) the wiring. Now the back up lights on my 2006 Dodge Ram 3500 stay lit when I plug in the 7 blade connector. How can I fix this, or what part/wiring kit do I need? Much tanks.
Reply from Jon G.
I would replace what you currently have with a completely new box like part # e99011 so that you can get rid of the bad wiring. I'm not sure what wire that diode is on but I would also try to figure that out and replace it with a higher-end diode like part # RM-690 if it was a single-light diode.
Jim S.
I have a 2021 VW ID.4 which come pre-wired for 7 pin connections, while the kayak trailer on has only 4 pins. What solutions are there
Reply from Jon G.
I would look into either using an adapter like part # TR20141 which just plugs into your 7-Way or by using a completely different connector like part # 30955 which plugs into your US Car Connector (when you unplug your current 7-Way from the back). This gives you both a 4-Way and a 7-Way so that you don't have to keep track of an adapter.
Jake W.
the 2003 ford psd wire colors are not the same as you are claiming. at least on my truck. i know. im trying to rewire a new plug in right now. keep blowing fuses.
Reply from Jon G.
The colors that we mention are just standard wire colors but they don't always match in real-world applications. As you've found in your situation you'll want to test the wires per function instead of just going by the color.
Shannon
How can I run a 12v fuel pump into a 7 pin and control the power from a uplifter switch in the cab of my truck Ford F-250 super duty
Reply from Jon G.
I'm not sure how you would make the connection to your uplifter switch and you would want to make sure that you have a circuit breaker or fuse to protect it, but what I would do is run 10 gauge wire # 10-1-1 from your uplifter switch back to the 12V power pin on your 7-Way which would be the pin in the 1 o'clock position .
Reply from Shannon
@JonG ok thanks I'll try it
Steve
I have a 2020 G M C truck I wonder can I use the light wire to charge my battery to my power winch it a lawn mower battery ? If I turn my lights on while running ? That the flat 4 plug .
Reply from Jon G.
The 12V power wire struggles enough to charge a battery with a 10 gauge wire so the smaller 16-18 gauge wire used for your trailer lights will not be nearly large enough to give your trailer battery a trickle charge. Your truck should have a 7-Way socket as well so all you should need to do is install a 7-Way on your trailer and route the power wire to your trailer battery. I recommend the kit # e99011 because it will help keep your wiring organized and make future repairs or modifications much easier.
Reply from Steve
@JonG thank you
Reply from Jon G.
@Steve You're welcome!
Ben
Without turning the mini van on I have full lights on, brake, left and right work perfectly. New cable harness. I need to disconnect the trailer connector to kill the running lights. Any ideas
Reply from Jon G.
It sounds like you have LED lights on your trailer. LED Lights are nice because they don't require as much power to operate but as a result sometimes they will light up dim when there is the smallest amount of power on those circuits. If you use a resistor like part # C57003 for a 7-Way setup or some that you install on the wiring directly, like part # DI34ZR , it should take care of your problem.
Bob C.
Hi. What is the best way to add a third brake light on a camper shell mounted on a 2002 GMC Sonoma SLS? I have a junkyard rescue shell that does not have a third brake light and will mount an aftermarket LED but I am not sure if a hot wire is available. Just need advice from more knowledgeable folks
Reply from Jon G.
Sometimes there will be provisions for 3rd brake light wiring somewhere along the frame but from the research I've done in the past it seems like there is no rhyme or reason as to which trucks have this wiring and which trucks don't. The best solution I have for you is to install the 3rd Brake Light Logic Module # PP20-702 . This is a very straightforward installation and will give you that brake signal that you're needing.
Edward R.
Hi! I have a 2012 RAM 1500 quad cab which has the standard incandescent lights. I'm building an Wind Stream 24ft utility trailer with LED LIGHTS. Question is "Do I need to have a converter to control the return voltage to control and protect the fuse panel in the truck?"
Reply from Jon G.
If you don't have the factory 7-Way and you're just wanting to install a 4-Way flat trailer connector for the trailer lights then I wouldn't say you HAVE to have a converter, but it does help to protect your truck so I do recommend using a wiring kit that comes with one like the part # 119178KIT .
Craig W.
I need to wire a four flat to the back of my camp trailer in order to connect to small aluminum trailer which already has a four flat. Any advice on this project would be helpful.
Reply from Jon G.
You can try to tie that into your current trailer wiring with a 4-Way flat like part # 18252 . One thing to be mindful of is that this will pull more power on those trailer light circuits so you might see problems there if there is too much power being pulled.
Reply from Gordon S.
@JonG if you still need to finish this project, might I suggest you run a four wire flat extension from the front off the travel trailer to rear along the frame and connect the small aluminum trailer to it. Use a Y-splitter at the truck tailgate and power both trailers independently. I was unable to post a couple of photos for reference. Google 4 Way Flat Y-Splitter Plug and Play Adapter Extension and Trailer Wire Extension, 20ft, 4-Way 4-Pin Plug Flat 20' Harness Extender Good luck.
Matt S.
Is there a ASME, NEMA or other standard that controls the pin diameter and spacing of 4-flat plugs? I have several trailers with 4-flat plugs and the spacing and diameters, while similar, do not appear to be the same, which makes it difficult to plug into some and loose connections on others.
Reply from Jon G.
I don't think there is a specific standard when it comes to the spacing and sizing for the 4-Way flat plugs - I think it's more of a "make your plug to fit like this so that it works with everyone else" sort of thing. You definitely aren't alone with this situation, which is why Hopkins came up with their Easy-Pull Harness that has a ring in the middle of the connector that makes it easier to remove when you need to. For a trailer end piece use part # HM48114 and for the vehicle end use part # HM48044 .
Butch
I have a 2001 Ford f250 super duty truck, I just purchase a sure trac enclosed trailer and moved to Florida. All the lights work on the trailer however I cannot get the Interior dome lights to work. I watched a you tube video to where a man said that his Chevy truck did not have the fuses installed in the fuse box, can anyone tell me what fuses I need to check and have installed? Any help would be appreciated.
Reply from Jon G.
You should be able to find this location in your copy of the owner's manual. When I looked online I believe the fuse you're looking for is in location 16 and is labeled as "Trailer Tow Battery Charge" and it sends back 12V power. You'll want to confirm this on your end too.
Reply from Steve
@Butch My trailer dome lights only work when the truck running lights are on.
Willie J.
Hey, I just brought a used Carry-On trailer with a 7way flat and it have three wires on the left side and two wires on right side running from the rear for clearance marker and tail lights . With only one oval LED fixture at rear on each side. Do I need a 5 to 4 converter? My truck is 2010 Ford F-150 with turn/brake is feed from the same wire.
Reply from Kef G.
It sounds like your trailer has a 7-way blade, and your F-150 has a 4-way flat. What you need to do is upgrade your 4-way flat to a 7-way blade with part # ETBC7 . This will give you the 7-blade trailer connector you need.
Bill F.
Need to go from 4 wire flat on motorcycle to 9 wire round on a can am motorcycle trailer. It is a 2018 Honda motorcycle.
Reply from Kef G.
There aren't any 4-way to 9-pole adapters, so the best way to get this working is to splice a 4-way into your trailer and remove the 9-pole.
Drew M.
I have 6 wires going into a 7 wire plug. None of the wires are blue and my electric brakes do not work. The only blue wire I see goes to a junction box on trailer w/black wire. How should I wire the plug? Should the black act as the blue wire? Very frustrating
Reply from Jon G.
While this article shows industry standards, it isn't a hard and fast rule. It sounds like you'll need to test the functions of all of your wiring and make your connections per function instead of per color.
Richard H.
I am rebuilding an old aluminum trailer and have purchased new replacement sidemarker lights. Because the metals react to each other and corrode, I have put a silicone gasket between the two metals. Will this cause a grounding issue? I have done the same with the new taillights. Thx!
Reply from Jon G.
If the grounds for the lights are not able to make contact with the trailer frame then yes, that will cause issues. To try to avoid the corrosion you're talking about I would try to ground all of the lights to a main ground line and route that up to your trailer connector.
Dan O.
Question, not sure if this is the correct location to ask a question. But here it is. I have a 1982 Sunline camper trailer. I replaced the standard bulbs with new LED tail and running lights. Their was green and white wires at running light locations. Here's the issue, when the running lights are OFF the turn and stop lights work fine. When the running lights are ON the turn and STOP lights DO NOT work.
Reply from Jon G.
Sounds like you either have a bad ground or short in your wiring. Check and make sure that all of your wiring (on both sides of the towing setup) is in good condition and that all of your grounds are secured to a clean, bare-metal surface. Attached is a link to a tiring troubleshooting article that you can check out.
Reply from Roger K.
@DanO I also ran into a simular problem with my vehicle when I converted to LED lights. I found the problem to be that the vehicle had a negative switching system which does funky stuff to the lights. I wired in relays to convert the negative switching to positive switching now I am having no issues.
Emmanuel A.
Hi there a have a small car dolly 7pins plug and the colors the my has is yellow Lt, white GD, green Rt but i am confused theres is one wire yellow/brown and green/brown i dont know what terminal are those TM or EB or AX. I need some help please. Thank you
Reply from Jon G.
What you're going to need to do is apply 12V power to those wires and see what happens when you do that. Brown is typically used for running/tail lights so that might be where those wires need to go, but you also need to make sure that you have the stop light covered as well (which is typically on the same circuit as the turn signal). The one annoying thing about wiring is that there are typical colors but it isn't an industry standard that everyone has to follow. This means if something doesn't quite match up (like what you're experiencing) then we need to do the testing.
Dave H.
I really don't like the Idea of "showing" electric trailer brake wire being grounded to the trailer axle. My axles move and is some what going to have a voltage drop when finding ground. My preferred method is to connect to the ground wire and keep the frame ground out of my schematics. By adding undetermined amount of resistance to the brakes you may end up with each wheel or at least each axle getting a different current flow and uneven braking. Thank you for having all this information quick and easy to find.
Reply from Gordon S.
@DaveH I agree for the most part. Just rewired a small utility trailer with a tilt feature with LED lights. I ran a separate ground wire down each side of the frame for each marker light and taillight from the same point I grounded the connection at the tongue. This way it does not rely on a ground at the pivot point, the lights maintain maximum power constantly.
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Source: https://www.etrailer.com/faq-wiring.aspx
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