F-150 7 pin connector battery charging

[jamaddox]

I have an F-150 Lariat with the Trailer Tow Package. I read somewhere that unless things were hooked up by the dealer the truck came from the factory without the connection to charge the battery from the 7 pin connector. I checked my dealer and they never heard this. Can anyone confirm this or has had to do it?

[Mustang65]

This was the case with the HD Tow Package option. There is a relay and fuse that gets installed in the panel mounted in the front of the engine compartment just behind the radiator. Just about everyone I know that purchased the HD Tow Package found their relay and fuse in the glove box. Why, I have no clue. If you do not have 12 VDC at your 7 pin plug (while ignition is on) Ford probably did not install the parts.
Don

[jamaddox]

How do I check this? I do not have an hd package but did have 3 parts in plastic bags as extras. I stupidly threw one away

[clubhouse]

With a multi meter you can check for current on the pins.

[Ela1948]

Originally Posted by jamaddox

How do I check this? I do not have an hd package but did have 3 parts in plastic bags as extras. I stupidly threw one away

With a multi tester or a 12 volt test light. Leave the truck switch on or the truck running while you perform the test. Get a good ground off of the frame or a clean bolt near the truck plug. The terminal that is just to the right of the cut out notch in your plug is the hot wire that feeds your trailer. It will only be hot when the ignition switch is on.

[Mustang65]

Here is a picture of the pin-out.
Don

[jamaddox]

Great thanks for the help. I have a multimeter but not used it as for now I am apparently electrically challenged. I have to read the multimeter manual

[wayfun]

Fords aren't the only trucks like that. On my Tahoe I had to connect a wire near the fuse box to make my 12V terminal live also. I don't understand why they just don't make the connection at the factory. What would it hurt.

[mcfarmall]

You should have a baggie in the glove box with a fuse and a relay in it. They go in positions 9 and 21 on the power distribution box that sits above the radiator when the hood is open. You must install them before towing if you want 12v at the 7-pin connector. I install mine in May and remove them in November as I learned on the F150forum.com that having voltage on the pin(s) will increase the likelihood of galvanic corrosion on them over time.

The other loose item you should find in the glovebox is a protective cap for the rear camera wiring harness (if you have the rear camera option). I use that one too as I remove my tailgate for the salty months...November through May.

Why remove my tailgate? Well, years ago I had an '85 Ranger and left my tailgate on year round. The tailgate lasted 6 years and was nearly disintegrated. Additionally, I have the camera in my tailgate and although they are designed to be weather resistant, I really don't have faith that they are designed to perform for the next 15 years without some kind of special treatment.

[RoyBraddy]

Check your manual and look for TRAILER TOW fuse and relay in the fuse panel mount over the radiator. That is where my 2010 fuse and relay had to be installed.. It seems to me my TRUCK battery charge DC voltage showed up on PIN 2 of the 7-way trailer connector when the iginition key was turned on with the fuse and relay installed... Your trailer side battery 12VDC voltage should also be on PIN 2 of the7-way trailer connector.

My extra package in the glove box had one fuse and one black relay relay in an unmarked plastic package in the glove box. I just checked and on my 2010 F150 FORD Truck the relay goes in position #9 and the fuse goes in position #21 in the power distribution box (fuse box) in the engine compartment mounted above the radiator.

My 2010 F150 truck did come with the trailer tow package with the built-in BRAKE CONTROLLER installed in the dash.

[Bassdogs]

Check the fuse layout info in your manual and ID the location for the 12V aux fuse/relay. When I picked up our first TT, the dealer installed the WDH and I remembered him getting under the hood and popping open the fuse box. Didn't understand exactly what he was doing, but when we headed home, we were good to go and the TT battery charge when we were on the road. A couple years later we purchased a new Chevy Silverado with the tow package. Didn't notice anything wrong on our first short tows for weekend outings, but noticed a low TT battery on a multi day road trip after 100's of miles of towing. My thinking was taken back to that original dealer install on the 150 and that diddling he did under the hood. Sure enough, a quick read in the manual when we got home, I quickly found the empty position in the box. The fuse/relay is one of the large speciality type so is a bit pricey, but found what I needed at a local auto parts store and the problem was solved. Its easy to trouble shoot and just as easy to fix if its a problem with a missing or blown fuse.

[jamaddox]

Thanks for all the feedback. I will check my owners manual to verify the positions. Still don't understand why the ford service department does not have a clue about this and why does ford not just do this at the factory

[Owen Stubbs]

I have a 2008 Ford Expedition with the HD tow package. I've towed a boat with it for years. About a year ago, I started towing a pup. Noticed the battery was not charging when connected to tow vehicle, but always suspected the wiring in either the expedition, or the camper.

Towed the camper with a friend's truck last weekend, and realized that vehicle DID charge the battery when connected. Thanks to this thread, I discovered I too was missing the relay and fuse. Luckily, both were in a bag with a wiring diagram in my glove box for the past 7 years!!! Installed and everything works as expected now!

[ecoboosteagle]

[QUOTE=mcfarmall;164941]You should have a baggie in the glove box with a fuse and a relay in it. They go in positions 9 and 21 on the power distribution box that sits above the radiator when the hood is open. You must install them before towing if you want 12v at the 7-pin connector. I install mine in May and remove them in November as I learned on the F150forum.com that having voltage on the pin(s) will increase the likelihood of galvanic corrosion on them over time

+1 if you google it there is a forum thread where a guy even post pics pointing to where the fuse and relay go in the electrical box. If you did throw away it shouldn't be an expensive replacement

[kjohn73]

Hmm. Interesting! We have a 2013 F150 with a built in brake controller. I did notice that there is no juice coming back when the truck is shut off, and just thought that is the nature of the beast. My old 97 Sub gasser has two batteries, one with a cut-off switch, so it will start if you use the switch, even if all the other batteries are dead. It had juice coming back running or not. I shall have to look into this. The Ford has only one battery, so I am not sure how badly I want to have its battery online when the engine isn't running. Decisions, decisions!

[Seann45]

Guys please remember that small a wire over that long a run makes it only a battery maintainer.. not really a charger..

[eng45ine]

Interesting information about the galvanic corrosion, maybe that is why Ford doesn't install the relay and fuse during assembly.

[Rockford James]

I found this out on my 2015 Lariat with max tow. My TT battery was too low to raise the jack. I figured I would plug it into the truck connector to let it charge a minute.

When I plugged in the trailer I noticed that the dash display gave me a notice that the battery was not charging. Sure enough, the jack didn't perform any differently when I tried it while engine was idling.

I then thought maybe if I increased the rpms it would make a difference. I sat running at about 1500 rpms for a few minutes and tried the jack again. The battery for sure got charged by doing this as the jack functioned close to normal. I speculate that the 2015 turns off power at idle or when engine is not running and kicks it in when at a driving rpm. I can't find anything to confirm this in the manual, but this was my experience.

My battery power indicator in my trailer also shows full after I drive it a while. When I picked it up from the dealer it was reading 3/4 fully charged. By the time I got home it was fully charged.

It would make sense that Ford added this to the new 150 with all the other changes and improvements. That would also explain why the new truck does not come with the extra fuse to plug in to make the 12v connector hot.

Again, I'm just sharing my own experience.

[RoyBraddy]

My complaint was the fuse and relay was in an unmarked small clear plastic zip lock bag. Had no idea what it was for... Then when I hooked up the trailer and found out I didn't have 12VDC there I looked it all up in the manual and noticed right away I was missing the plug in fuse and black relay. Light in head then comes "ON" what the two units in the bag was for.

Roy Ken

[jamaddox]

Though I replied to all so sorry. I did find the baggies in installed them. I guess everything is working. I am seeing corrosion (I think) because some of the pins on the trailer plug and on the truck are green. Anyone know how to prevent that