bing tracking image
Q & A Icon

Troubleshooting Lack of 12V Power at 7-Way Trailer Connector on 2019 Ford F-150


The 12 volt #4 is not hot on my F250 2019. I looked in the owners manual and does not clearly specify which fuse it is. Yes I tested it when the. The truck was running. Thanks


Expert Reply:

Since you are not getting the 12V power when your truck is running, you most likely don't have a fuse issue as you stated their isn't a specified fuse or relay in the owners manual. The issue is that your truck is computerized even at the 7-way. It can sense when a trailer is connected based on the voltage draw so it won't sent a signal for 12V when using some testers, especially LED testers because there isn't enough of a power draw.

The system requires a power draw on the 7-way and then holding the brake pedal for about 3 seconds until your dash registers "trailer connected". At that point, the vehicle will deliver the 12V power to your trailer connector and not before. I recommend using a circuit tester like # PTW2993 to test for the 12V power once you get that "trailer connected" message on the dash. That 12V power will be on the 1 o'clock pin location on the 7-way so the corresponding wire will need to be probed to test.

click to enlarge
expert reply by:

Products Referenced in This Question

Product Page this Question was Asked From

Follow up Questions

Les T.

Like Lee, I have a trailer I pull with 2 different trucks. I have a 2012 F350 I pull a travel trailer, and also at time pull a lowboy with. The lowboy, I use a 7-way plug, 4 wired because my lowboy does not have brakes.. No issues at all with the travel trailer or lowboy lights. All work fine... on the F350 I also have a 2019 F150, and when I plug the lowboy into it, only running lights work. No blinkers or brake lights... weird.... I'll check and see if mine is the same as Harley W's...

Reply from Les T.

@ChrisR I searched the manual and found the fuse for the lights. Pulled, and it is fine. Went ahead and even replaced it. Still no go.. SOOO I went ahead and bought a MICTUNING 7 Way Blade Trailer Connector Tester with Red LEDs. Everything works great on my F350. Does not work on my 2008 OR 2019 F 150's..... No blinkers or brake..... More digging to do.....

Etrailer Expert
Reply from Chris R.

@LesT Hmmm. I wonder if it's just an issue with the factory wiring. Try and test the wires behind the connector to see if you get any power there. If you do - then the connector itself is bad and just needs to be replaced. If not - I think it might be worth it take a trip up to a local Ford dealer to have them take a look.

Reply from Les T.

@ChrisR Got it. If you unplug the auto engine off (where the motor shuts off at red lights) it messes with your trailer lights. I plugged that back in and everything works... Weird...

Reply from Mspenc45

@Lest Also, be aware, as I found out the hard way, your trailer 12+ will not get power with the driver door open on a 2019 Super Duty! Procedure for ensuring power is, close driver's door, depress brake, start truck, hold brake while truck recognizes trailer, click OK until you get through any notices like "Trailer Detected" etc.

Reply from Joe

@Mspenc45 I just purchased a 2020 f250 and long story short. My 12v to trailer doesn't work unless the key fob is in the truck with doors shut. Don't like it and don't understand why they designed it that way.

Reply from Scott

@Joe THANK YOU GUYS for this thread!!!!!!!! I have been screwing with the "intermittent" 12V trailer pin on my 2019 F150 for hours, testing and changing fuses reseating/cleaning pins and taking apart trailer batt charge circuit and done lights etc etc etc. So frustrated I googled while having lunch and this came up. You guys are absolutely correct if EITHER the driver's door is open OR the keyfob is in my picket outside the truck, the 12V shuts off!!! Lights, signals all continue to work. What a freaking disaster idea from Ford. Thanks boys.

Reply from Hank A.

@Joe unreal I have been driving myself crazy fuses wiring harnesses contact cleaner etc. I go out now, hook up trailer, shut truck off turn it on set the trailer accept trailer and the inside lights work.....I only pray this is figured out. Thank you very much.

Reply from Darius S.

@HankA Thanks for this thread, I thought I was losing my mind. What I also noticed on my 2018 F150 is if you depress the brake pedal, you can hear a relay cycle and the interior lights of the trailer turn on, release the brake pedal and 2 sec later the relay cycles and no power inside the trailer, effectively disabling any power at the 12v pin...what a messed up system. Anyone else experienced this and if anyone has had success in having dealer adjust programming or someone wired in a constant feed would like to know. Thanks

Reply from Samantha

@Mspenc45 THANK YOU. This solved a huge issue for me. I tried everything short of closing the dang door. So simple... Start vehicle, plug in camper, SHUT DOOR, hold brake for three seconds. Viola, power.

Etrailer Expert
Reply from Chris R.

I'm pretty sure the F-150 just has a blown fuse under the hood. Check your owner's manual for the appropriate fuse locations tied to the trailer turn/brake lights and replace them to see if that resolves the issue.

Reply from Rick L.

@Mspenc45 Perfect, got it, appreciate your response, it only took 2 years for me to figure this out??

Reply from Mspenc45

@RickL Start the truck, plug in the trailer, or plug in and start the truck. Close all truck doors, hold the brake for 3 seconds. Leave the keys in the truck, running or not, doors closed and you should have power.

Reply from Rick L.

@Mspenc45 So I same truck as you, there is a lot conversion about this topic. But I want to know how and how to get power to trailer to operate jack without battery power. My 2005 did it automatically when plug was connected, my buddies 2016 does it. The trailer, without the battery will not operate jack even if hook up to 120v. Can't figure this out, they changed something ...I think I'm going to run a line from Uplifter Switch to the rear

Harley W.

Lee is correct. And they are NOT universal. My Dodge 2500 is different from my F150. Power and Ground are the same but Left, Right, Tail and Backup are all mixed up. Ford claims they conform to a SAE standard. I'm thinking I'll need some sort of converter/translator to use with one of the trucks! Grrrrr.... AND Ford has built in a whole raft of conditionals to make a trailer connection; all of which are enforced by the accursed Body Control Module. Bureaucracy on four wheels!


I have both a 2017 and a 2019 F150 that I want to tow my 2019 Jeep Wrangler JL with. I have installed the Mopar K6862742 factory wiring harness to flat tow the Jeep. When I plug the Jeep into a Dodge Ram 1500 all of the lights workbrake, signal, clearance When I plug the jeep into either of my F150’s nothing works.................I thought all 7 way plugs were universalThanks

Etrailer Expert
Reply from Chris R.

The specific pin function locations on a standard 7-Way are universal, so I'm not exactly sure why the harness isn't working on your F-150 trucks. It would be odd for both to have a blown fuse - but it wouldn't hurt to start there. You might also test the 7-Ways with a circuit tester just to be sure everything is working on the truck's end. Do you have the ignition on in the F-150 when testing the lights?

Reply from Idahodave

@Lee The Mopar harness uses the +12v from the 7way connector to switch a relay that connects the tow vehicle signals to the JL lights. No +12 and it doesn't work. Seems the Ford needs to sense to a load on the 7 way before it supplies +12 to the 7 way connector. Mine works on a 2019 Ram but not my 2017 F550 motorhome.

Reply from Jason S.

Jason S Your etrailer trouble shooting tips are well value your team has been very help full and knowledgeable Thank you etrailer for being out there

Reply from Randy S.

@JonG Ford Dealerships do not know anything about this I have been to two of them today and they look at you like you are talking jibberish when you give them all this info- which is much more helpful than they have been. Nice guys but you would think they would know something about it

Reply from John T.

@RandyS I have a 2020 Ford F-150 and pull a 18’ [email protected] trailer. My [email protected]’s fridge will run on 12V, AC and propane. Whenever we pulled with our 2020 Jeep Grand Cherokee we powered the fridge from 12V ([email protected] has batteries as well). I understand the Ford 7-pin doesn’t provide 12V until it detects a trailer connected. So, how do you actually test that 12V connection? This is our second trip with this truck and our [email protected] What we are seeing on occasion is whenever we stop and power off the truck (fueling stop etc), the [email protected] doesn’t automatically switch to internal batteries as it has done in the past. We get an error on our fridge that we don’t have sufficient battery power (yet our solar battery system shows full charge) and our LP monitor flashes (will do so if it detects low batteries). As soon as we power the truck on, everything goes back to normal. I’m 99% sure it’s the 7-pin on the truck

Etrailer Expert
Reply from Jon G.

@PhilH That would be more of a Ford dealership type of question/action since it is connected to their computer system. You could potentially bypass this by routing your own power wire to the 7-Way but I'm not sure how that would effect the Ford system.

Reply from Phil H.

@JasonS is there a way to turn off the computerized control on the newer Ford's? With ours, you have to have truck running and the trailer recognized to use the interior lights and the landing light. Very annoying when you are trying to load a horse.

Q & A Icon

Similar Expert Q&A Pages

See More Q&A Expert Answers >>