2016 Ford F150 - Trailer Tow Battery Charge Problem & my Fix

Details of what I feel is a design flaw regarding 2016 Ford F-150 Trailer Tow Battery Charge circuit that is basically non-functional and what I did to correct the problem.

[@va3kv]

I implemented the mod last summer on my 2015 F150 and so far it has worked great. I just got back from 3 months of RVing across the southern USA from Florida to California and its worked flawlessly. I don't need to waste propane as it allows me to run the RV fridge on battery, with no worries that the trailers battery will run low or the rooftop solar panel not keeping up. There is about a 1 volt voltage drop in my wiring harness as I get a steady 13.5 volts at trailer battery. Thank you very much for a great mod.

[@donbedford3443]

Thank you for the comment!

[@RDB83052]

Update - I towed my R-pod 180 camper for 3000+ miles on vacation and the new circuit modification worked great keeping the campers dual batteries fully charged while running the campers refrigerator on 12 volts at the same time. That's how the circuit should have worked from the factory!

[@themathdude]

Just adding my voice to those who recently bought an expensive 2016 with the expectation that it would charge the trailer battery just like the car we just traded in. Well more $$ and a day plus of my time will fix this properly so thanking your profusely for this well done and clear video and shame on Ford. What did they think people were going to do with a pickup truck that came with a MAX tow package, why they were going to tow their travel trailers that have batteries.....duh.

[@themathdude]

Thx again! I just finished installing a 10 amp wire with split tube (across the cab firewall below the hood opening, then down the drivers side by the power brake diaphram, along the frame and over the tank zip tying it to the slip tube that is already there. I used an empty terminal on the buss bar (under the plastic next to the fuse panel) rather than direct to the battery. I installed the pollak connector too (see below). I used just a 30 amp inline fuse near to the buss bar. I decided not to incorporate the relay and original orange wire since I had trouble getting that circuit to recognize the trailer anyway, so as a result my trailer pin is always hot. I may at a later date add a relay to a circuit that comes on with the key but for now it's ok since I have a car battery protector installed in the trailer that will keep the car battery from draining if I don't disconnect the truck. As to the pigtail. I unplugged the connector at the socket. I then removed the wrapped electrical tape then unplugged the connector at the other end near the spare tire. I then cut the large gauge white wire near the fender and also a small blue wire going to another circuit so I could remove that connector. With the complete pigtail removed I cut all the wires about 5 inches from the"spare tire end" connector. I then cut the new pollack pigtail to a matching length and spliced in the wires. I used blue (14-16) butt connectors for all but the black and white wires where I used the supplied yellow 10-12 connectors. The colors all match except truck yellow goes to pollack red, and truck grey goes to pollack yellow. The pollack black will go to new wire you run from the engine compartment. I put split tube on everything and buttoned up with tape and rehung with zip ties. Looks great like it came from the factory that way (and should have!!!!) It's all fine all the lights work on my trailer and the trailer charge circuit is now operational and good to go! BTW I ran an extra 14 gauge wire in the split tube since who knows when one might need another 12v circuit at the rear end in the future (like for a canopy interior or back up lights, etc.

[@RDB83052]

+David - wiring the TT Charge circuit to be “ON” all the time there is hi risk of draining your trucks battery if you do not disconnect the trailer from the 7-pin connector whenever the truck is not running. I added another comment explaining the logic of the orange wire. Sounds like your wiring is working great, but I would recommend getting that relay to work. I think you were there but the sequence of events needed to energize that orange wire was not met therefore the relay was not working.

[@richarde735]

I also decided to purchase SAE J1128 - # 8 gauge to go from the battery, through the 20 amp breaker, the heavy duty 12v 100A relay and to the back bumper. the entire run is wire loomed and fished through the truck frame (the passenger side is shorter FYI) . I managed to get five cable ties on the wire loom through the side holes along the frame so it's just not bouncing around inside the frame. I don't know if I mentioned this but I'm not charging a battery. I am powering 234 watts / 19.5 amps worth of LED lighting on my back bumper and boat trailer (I get there in the dark, flip the switch and it's like daytime at the boat ramp). My older F150 has this setup and it runs great on the factory harness but I didn't want to harm the harness on the new 2016 F150 with the small OEM harness wire size. Had it not been for this video... I'd might still be searching for a solution.

[@richarde735]

I purchased a Pollak PK 11-998 (as outlined in the video) and I have taken that a step further... I didn't want to cut into the OEM factory harness so I also purchased a Pollak PK 11-934 and made a short sacrificial jumper between the factory connector and the back side of the bumper trailer outlet.

[@armstronglance]

Thanks for posting this! Ford really screwed up with the small wire gauge. ("Ford has a better idea"). My guess is with all the lights on, they dont you pulling 12amps more amps from the alternator. I have the same truck, with tow package, it's only 2mos old. We sold our motorhome, and are looking for an RV trailer. Looks like I'll be doing this upgrade.

[@PhilTylerTX]

PERFECT solution! VERY clear and thurough. I'm a little too close to my next towing event to do this, but I'm ordering the connector now (I have the relay and CB). I've noticed that if I plug in my trailer while the truck is running, the TRM will not activate the 12v charging line. IF, however, I have the truck OFF, plug in the trailer, then start the truck, all seems to be fine. 2016 Limited btw. Does this sound normal?

[@donbedford3443]

Not sure if that is normal, but my truck only activates the Trailer Tow Battery Charge circuit when I place the transmission into a gear. The circuit then appears to stay energized until I turn the ignition OFF. When I installed this modification I wired in a 12 volt LED powered by the orange wire to determine the logic of that circuit and to verify that is was ON. I located the LED in visible spot between the rear bumper and the fender. It’s only visible to the person that knows its location. I probably should have detailed the wiring and location of the LED in the video…maybe I’ll try to edit the video.

[@wefoundadventure]

Thanks for the video. We have a 2016 F150 and are finding that the battery is dying when we tow while running the fridge off 12v. So if we make the modifications you recommend it should work? How could they have such underpowered wiring in the truck!? We were towing previously with an Explorer and it charged the battery while running the fridge no problem.

[@RDB83052]

+We Found Adventure - I completely understand. My brother’s 2013 Ford F150 TT battery charge circuit works properly. On his truck the wiring is sized correctly, it’s protected with a 30-amp dedicated fuse, and is controlled via relay similar to my modification only its factory. Why Ford would re-design the circuit to be non-functional is beyond words….it’s brain damage! When you purchase a new truck you don’t expect these types of problems. I have a career of expertise in equipment controls. I retired from a fortune 500 Company after 35 years of troubleshooting, designing and installing equipment controls ranging from simple circuits like this to very complex control systems that have thousands of I/O over multiple communication networks. I would like to know their logic, reasoning, and the issues that drove the circuits re-design. My wiring modification provides 30 amps of service to the trailers battery with minimal voltage drop. So, if your trailers amperage load while towing is less than 30 amps this should solve your problem. Thanks for your comment!

[@dancarroll2049]

Great video ' I have 2015 F 150 ' and my screen is telling me trailer tow battery is not charging?? So now I will pull the harness and install a thicker gauge wire ' thank's for the tip....

[@RDB83052]

Dan - Installing a thicker gauge wire by itself may not help much. Not sure about the 2015 F-150, but on my 2016 the “Trailer Tow Module” controls that circuit so a heaver gauge wire will definitively reduce the voltage drop but I’m not sure if Trailer Tow Module will support more amps. Let me know how it works…

[@dancarroll2049]

Good point' I will do the same connection 30 amp circuit breaker and a 40 amp relay with the 12 gauge wire harness....hope it works?? If not I will be calling the dealer...it seems to be a on going problem ?? I have other issues with the censors But besides that it's great truck for towing..more power then glory l o l .. I will let You know either way.... Thank's...Again..good video...

[@themathdude]

if you just blow off the orange wire all together forgetting the relay that cirucit will be "outside" all trailer tow module stuff. Just need to be sure your trailer has a car battery protection device and your remember that pin will alway be hot. I wired up my Suzuki and trailblazer like this and it worked fine.

[@dancarroll2049]

David Kebler Thanks for the tip ' will try that if it acts up again' but for now it's not giving Me any problems ? Had a lot of dirt in the connector at the back of truck as I travel on rough gravel roads with my trailers..so far so good ????

[@theomerian6102]

This is a great video and a must view for anyone that plans on doing any serious RV-ing with their F150. I'm planning on performing this mod once the weather warms up a bit (I live in Illinois). My question to you is does doing this mod have any negatives? Does everything still work in the trailer status display? My 2016 is a Lariat - I'm guessing yours has the fancy display too? Anything else to be concerned about? Thanks for posting!

[@RDB83052]

Theo, Thanks for your comment. I have towed my camper over 10,000 plus miles since the mod and I have had zero problems…it’s worked perfect. The reason that I designed the circuit this way was so that the Trailer Tow features would still work as designed from the factory. The only exception is that now I have 30 amps of power to the trailers battery with very little voltage drop. All of the instrument cluster features for the “Trailer Tow” will still work as designed.

[@themathdude]

where do I locate the factory wiring harness? Is it simply the connector in the rear of the truck to which the current harness is connected?

[@RDB83052]

You are correct. The factory wiring harness is connected to the plug (the one that needs replaced) that powers the 7-pin tow connector. When cutting the plug from the harness leave as much harness length as possible to make splicing the harness wires to the replacement plug easier.

[@casmered]

Spoke to a tow wiring shop today and they suggested just going a straight drop from the battery to the back. Is there any reason not to do that? I want to forward them your video, but they did my other car a few years ago and it works great. They are essentially suggesting doing the same thing as then. Run a hot wire back. Just wondering your thoughts. Thanks.

[@RDB83052]

@ casmered - There are a couple of reasons for NOT running a hot wire directly from the battery to the 7-pin tow connector. To begin with, a non-fused “straight drop” circuit is a fire hazard in the event of a short circuit. Second, if your tow vehicle is not running, and you fail to disconnect the load your tow vehicles battery could be drained. Ask yourself, would anyone allow an electrical contractor to wire the circuits in their home directly to the main feeders bypassing circuit breakers or fusing…I don’t think so. All electrical circuits need fuse protection at a minimum, and in this case the addition of a switch or relay to control when that circuit is energized. Final thoughts…do not use that wiring shop!

[@casmered]

RDB83052 thanks for the quick reply. I should add that I overlooked in my statement he was talking that he would also use a solenoid that was key activated in the wire. Not sure if that makes any other difference.

[@RDB83052]

A solenoid, relay, or switch all do basically the same thing but offer no short circuit protection. I would ask him to incorporate a fuse or circuit breaker to protect the circuit from a potential short. The design of the circuit will then be very similar to mine in this video. The reason that I used the orange wire to control the relay/solenoid is because I wanted the circuit to function as it was designed from the factory since it was a new truck, but wiring the solenoid to follow the logic of the keyed ignition is fine too.

[@richarde735]

the new harness I ordered should arrive today... I'm curious if the main 20 foot harness going forward to the front of the truck is undersized as well or is this just an issue with that last 12-18 inch short jumper from the main harness to the trailer outlet on the bumper?

[@RDB83052]

Richard - On my truck, the trailer tow battery charge circuit is an 18 gauge orange wire without dedicated fusing. The orange wire is 18 gauge from the firewall connector under the hood and continues back to the 7-pin tow connector. So yes, it is 18 gauge in the 20 foot wiring harness. I should clarify that Fords wiring size for this circuit is correct for their design, but their design is non-functional. Their circuit is controlled by the Trailer Tow Module located under the dash so even if their wire was 10 gauge I doubt if the Trailer Control Module would support 30 amps. The modification that I have provided uses the logic/control voltage from the Trailer Control Module to control the new 30 amp circuit. This was the least expensive and simplest way for me to make the circuit functional.

[@themathdude]

yup that's trure it's 18 gauge all the way.

[@RDB83052]

The orange wire must be energized to power the relay for the new circuit. The Trailer Tow Module controls the orange wire, and on my 2016 Ford the logic for that circuit is; 1) The Trailer Tow Module must detect that a trailer is connected to the 7-pin Tow connector 2) The transmission then must be moved from Park to a gear to energize the orange wire Also, the instrument cluster inside the cab can be helpful for troubleshooting because it will display a message regarding the status of the 7-pin Tow Connector if a trailer is connected or not.

[@themathdude]

for others wanting to do this here are links to amazon for items breaker www.amazon.com/gp/product/B004AHAD2E/ref=ox_sc_act_title_1?ie=UTF8&psc=1&smid=ATVPDKIKX0DER relay www.amazon.com/gp/product/B01FLK0E36/ref=ox_sc_act_title_2?ie=UTF8&psc=1&smid=A1WDKHESM7DAAM pollack harness www.amazon.com/gp/product/B0031XUKQW/ref=ox_sc_act_title_3?ie=UTF8&psc=1&smid=ATVPDKIKX0DER