How to Wire a 7 Way Trailer Plug (It's Easier Than You Think)

I have a set of LED tail lights that I want to put on my old old... OLD caravan. Had a quick attempt before I left on holiday, but everything I tried was a bit of a disaster. Lights flashed and there was actually sound as well. We have had problem for a while each time I connect caravan with the tailgate brakelight flashing. After we hold the brake pedal, this stopped and I always assumed it was holding current somewhere because of Redarc brake controller. But this problem is keeping me baffled. Have always done my own wiring, often running heavier wire than required. Done this for many years and want to change all the lights on the old girl once I get my head around what is happening. See there are units that add resistance to a light but how do you know which one to add. My friend has unit on his drawbar that has the standard wires enter an aftermarket box. We were going to see what is in box because it did same thing. The box is actually sealed shut with gland nuts on each end. I am sure I could do a similar unit if I knew what they have done. Any ideas would be appreciated.

I am wire from go on a 2013 trailer, enclosed 16’. From reading your comment to another regarding relays, My assumption would be 1 relay each, left turn, right turn, running lights, reverse lights, and a general one for any switched LEDS; OR JUST THE FIRST FOUR:?

Hello on trailer side 7 pole plug flat i have white ,red green and two black wires one of the black is heavier gauge than the other one which wire goes where if u don't mind me asking the wire got hang up on the bumper hitch and pull the ires out of the socket wiring is 4 a gooseneck thanks

We have a 2022 Dodge Durango, the running lights went out. Fuses look good, I haven’t tried the circuit tester yet. Our trailer is a 2021 Keystone passport. Replacing the 7 way plug, is this fairly easy to do? Is there something I’m missing on why the running lights went out? Blinkers, brake lights work. Any help would be great.

Great website! So I have the 2015 f150 Platinum and an old 92 fifth wheel, I started changing out the old trailer lighting for LEDs, I did the front two side marker lights and everything went fine, last week I changed out the rear top red marker lights and one side amber marker leaving only the two tail lights and one side marker to do the next day. I plugged them in and I got nothing, after testing everything, working backwards checking fuses and grounds, I got nothing. I began to surf the internet for answers and the only thing I could come up with was that it was a Ford thing and even they didn't know what to do. I'm a full time RVer so by the time I get a chance to work on the trailer after work it's pretty much starting to get dark. Last night I found this site and read the whole entire feed! Not only did I learn a lot! But towards the end of the feed someone had my situation and you explained it! I get that the LEDs confuse the computer and it thinks I have bulb's out and/or it thinks there's a problem with the trailer lighting module but if i finish changing out the last three remaining lights will I still have the same problem and have to put the old ones back on? I may have missed something on it last night if you already said, so I apologize in advance if you did. Thank you! ~QMel~

I have a 2021 F250 and when backing our boat trailer the surge brakes are locking up. We never had this problem when pulling our boat with our F150 so I am trying to figure out what is causing this with the F250. Any suggestions?

My 7 way harness was stolen from my 2021 Keystone Springdale SG300BHFW. I have purchased a new harness but have no idea how to wire it back.

Just rewired (7 pin) a preowned horse trailer we bought. Electric brakes work, running lights work, brake lights work. When you turn on a signal indicator both sides flash like hazards. Haven’t even gotten to accessory lights yet. What have we done wrong.

I have a 2018 F-150 XLT that did not come with the factory tow package. I had to run a power wire with bus under the hood to the rear 7-pin harness in order to power my Curt Echo wireless brake controller. I want to install the Tekonsha P3 brake controller inside the truck now. Do I keep the 12v power to the rear 7-pin harness, and add another power wire with bus/fuse under the hood to power the Tekonsha controller? Or, do I need to remove the power wire to the 7-pin harness and use that for power to the new controller? Will it be safe to keep power to the rear harness? Thanks.

If this is not the right forum please redirect me. I just learned my 2018 F-150 SuperCrew with a tow package will not charge the trailer batteries while driving. The RV dealer checked the 7-pin Aux 12V and it showed no power. I spoke with a Ford service tech and he stated in order to have power the truck needed to be parked and you had to keep your foot on the brake pedal. He then hooked up a device that simulated a towed trailer and when the brake was not pressed there were zero amps at the 7-pin., but when the brake was pressed it showed 6-7 amp at the 7-pin. What are your thoughts about running a 12 or 16 gauge wire directly from the tow vehicle battery to the 7-pin Aux to charge the trailer batteries while driving? Would you recommend a DC to DC charger to up the amp output? Thanks.

Greetings I have just finished wiring an old trailer to the diagrams(sae) and I have a curious issue I tested the truck to find the correct pin location and tested the trailer with a starter box and each works properly separate But together the trailer turn functions work correct only when the running lights are off but when the running lights are on the entire system will blink on and off or actually dim up and down The trailer lighting is grounded to the trailer at the lights single wire leads at the clearance lights, 2 at the tail lights and a lead passes to the truck from the frame other trailers work correctly on the truck as well what should I test next?

I have a 2021 Subaru Ascent with factory tow hitch and both 4 pin and 7 pin connectors. My question is, can I wire my Harmar Scooter Lift electrics to the 7 pin, assuming the black battery wire provides always on power to the lift?

Regarding the 12 V to the trailer. We just bought a 5th wheel. I saw in the manual that this 12 V will feed the trailer 12 V system. Is this supposed to be conected directly to the tow vehicle battery? Thanks

I'm trying to help my cousin remotely. He has a 2002 Chevrolet Tahoe with a tow package, including a 7 pin connector. He also has an older model utility trailer. While visiting with him last week we replaced the lights & harness on the trailer with LED lights. The harness that came with the lights only has 4 wires. I believe we hooked up the lights to the wiring harness correctly. We used individual frame grounds for the side marker lights and the rear lights. The rear lights only had 2 wires. He has an older 7 wire to 4 wire adapter but it doesn't seem to work with there LED lights, unless we wired them up wrong? Do we need some other kind of adapter? Any help or comments would be greatly appreciated.

21 Denali and 21 Months Branagh 3760. I damaged my plug on the trailer and while replacing it I discovered that RV wiring is a different layout. Do I have to have my truck hooked up to probably test ?

When we hooked lights up to the trailer the right blinker worked independently. When left blinker was activated both the right and left blinker came on. And the right headlamp on the trailer was on when everything was off. We inhooked the trailer and started at the plug on the truck and the red wire and green wire are hot all the time. We cut the yellow wire above the plug and that acted as it should not hot unless blinker is on. Above the plug we cut the green wire and it was hot when blinker was on and off . 1. Should both wires be hot ? 2. Why do both blinkers come on with left signal? Any help is appreciated Thanks Was working fine. Plug mount on truck got bent a little but wires look good. I guess first I need question 1 answered Thanks in advance

I have a 2020 Ford F150 Raptor. When I connect my RV to the 7 pin plug it does not charge the battery on the RV. RV service center says it's the truck, Ford says it's the RV. Any idea who's right and or how do I get it to work ? When I had a Ford F250 super duty everything worked the way it's supposed too.

Does the chassis of a utility trailer have to be connected to the vehicle ground for safety or any other requirements? The ground wires of all my trailer's lights are wired directly to the junction box connected to the 7-way plug, so a path through the frame is not electrically necessary.

The black battery wire should be same size as the white ground wire - 10 gauge in chart - faq311-7-way-trailer-diagram-rv_2_800 The picture below this chart shows correct wiring for RV plugs. As a professional RV transporter I have seen to many trucks wired with those 2 wires to small and cause a fire from overheating. I built my own wire harness and none of the RV wiring was connected to the factory wire harness except the battery and brakes. My harness uses relays and 30 A circuit breakers. No problems since 1998 with my RV harness.

7-Way Trailer Wiring Color Code RV Standard You have an error on this chart. The RED is left turn not a 12 v battery wire Anyone who wires their RV 7 blade plug according your chart will suffer so problems with no left turn or left stop light. the rest of the connections are RV standard connection with Yellow being optional.

I'm wireing a semi trailer and have three tail lights per side,the lights are marked ground/tail/stop,turn. White is ground brown is tail green is right turn,I have a red wire for brake but if hooked up to turn/stop wire it works but not together so what is wrong. Another words turn the blinker on fine but hit the brake it canceled the turn

I have a travel trailer and the rear lights have only one bulb. I would like to replace with a two bulb light so that I can have back-up lighting. Is this possible or is my travel trailer not wired for backup lights? I have a 7-way connector from my pickup truck to the camper.

Thanks for the quick response. I was also directed to have another vehicle with a 7 way connector try to provide power to the camera. I used a 2007 GMC truck with towing package that also didn’t work.

I have a Ford F 250 with towing package. I recently purchased a 2020 Dutchmen Kodiak Camper that has a built in wiring harness for a rear view camera (Furrion). Simple installation but can't get power to camera, called Furrion Tech Support and was told camera only gets power when headlights are on in manual. Tried, didn't work. Then informed that some car manufactures have current limitations on newer vehicles and that I can buy an adapter cord to solve the problem. Doesn't sound right?

I have an enclosed trailer with great 12 volt DC interior LED lighting. It sits next to the garage and I do a lot of work in it. What’s the best way to Connect 120 volt AC power to run the 12 volt lighting? Currently I just hook up the truck when I need to use it but this is getting old. Is there a way to run a converter to the 7 way plug on my trailer?

I have a 2002 Chevy Silverado 3500 at my company. Its got a trailer attached to it, but doesn't work. I've been trying to fix it and I notice that its wired wrong(7 wire harness). Also, there's an auxiliary battery near the trailer neck which is connected to the junction box ( meaning two wires from the truck harness itself aren't connected to the junction box). All the wires from the trailer are connected to the junction box. Is this auxiliary battery necessary?

Hi there, For people that already have a 4-way connector (e.g. by using Curt 55370) how would they go converting that to use 7-way connector and in particular something like Hopkins HM11141144? BTW HM11141144 is the best connector I saw with OEM like quality. I got that the +12V and ground for HM11141144 will come from the battery. Also the backup trailer lights will come from the car backup lights. I see how all the other trailer lights will come from 55370. What is not clear is what should be done with the trailer ground wire on the 4-way connector out of 55370. It cannot be used for trailer ground because it cannot carry enough Amps (55370 it's protected by a relatively small fuse). For trailer ground I already got the 10 awg wire from battery. Should I just ground that wire? Thanks

I have a 2013 Chevy Pickup 4-wheel drive. I hooked my trailer brake controller. It was working fine. Then I tapped into the power wire going to the controller, to power an emergency light. Just recently I reworked the wire connection and shorted out the power wire. Now I do not have power to the controller and no power at the two terminals at the front of the fuse box under the hood. The fuses look good at the front of the fuse box. Would anyone have an idea what the issue is.

I saw both 20A and 30A specified for the +12V Red wire with the mention that 20A will only be good for 2 and 4 brake magnets. My car towing weight capacity is max 3000lb and 200lb tongue weight - small, so the campers I'm looking at are small. So 2-4 magnets will be enough braking for me. Is there a way to find out how many magnets a trailer has? Is there a rule of thumb like one wheel one magnet?

I would like a clarification on the wiring. I have a car that has a hitch harness in the trunk (power directly from battery, turn RH, turn LH, brake light, tail lights, ground directly to car body). I do not want to install any brake controller in the car. I plan to use a wireless one like Curt C51180. So in this case do I need to hook anything up on the Blue wire (electrical brake controller power output)?

Very nice article. I would suggest adding a note that for the section at the end Soldering: This is the best way to connect wires. Simpy solder your wires together for the strongest, most reliable connection using a soldering gun. Use heat shrink tubing to protect the soldered connection. that its always important to have the right length enough to give a good overlap of the insulation after soldering and size just a little larger than the insulation, for a tight fit of heat shrink tubing already on the wire prior to soldering them together!!! Its easy to solder first and then go Hmmm... now how do I get this tube over my wire?

I would like to know how to best replace 2012 jayco 266RKS PULL behind 2 axel brake wires at wheel hub that tire blowouts made into spaghetti.