Question Flat Towing and 4-pin/6-pin/7-pin plugs

[DeltaNu1142]

Hello RVF!

I joined this morning to ask an electrical question. I'm an electrical guy... I do all my own wiring. I'm setting up a vehicle for flat-towing, and there's something I can't get my head around.

My tow vehicle (Ford F150) has OEM 7-pin and 4-pin sockets. They both work just fine for everything I've needed to tow.

As part of all of the flat-tow gear I've amassed, I have a coiled 7-pin to round 6-pin cable. Both ends are female. It looks like this:

7-pin goes to the truck; 6-pin, by process of elimination, goes to the towed vehicle ('05 Jeep LJR, for what it's worth).

Yesterday, I wired up my towed vehicle's tail lights to a 4-pin plug using a harness sourced from Curt... it tests well, plugged directly into my truck. It has three exposed male pins and one female pin... this one, exactly:

Everything makes sense so far. This is the plug you'd expect to see on a trailer/towed vehicle.

Now... because I'll be using a supplemental braking system, I want to keep the towed vehicle's battery charged up. But I don't need the reverse pin--and the 7-pin plug is huge--so I've decided to install a 6-pin socket at the front of the Jeep. It will have to be the opposite gender of the coiled 6-pin end... so, male exposed pins. This is where things get weird.

This is what I found to install at the front of the Jeep:

This is also supplied by Curt, and they call it a 4-way vehicle-side to 6-pin round adapter. It's very obviously intended to have the 4-pin plugged into the tow vehicle, with the loose wires connected to power/ground/brake on the tow vehicle, and provide a socket with male pins to connect a cable to the towed vehicle! But... my coiled cable has female pins.

Electrically... I have no problem with this. I'll snip the 4-pin to 6-pin adapter, add the other-gender 4-pin plug, and install it on my Jeep. The small end of my coiled cable will plug into that. But from a compatibility perspective... what is the deal here? Am I totally misunderstanding how these plugs are supposed to be used? My 7-pin to round-6-pin cable isn't a unicorn... it looks like the blue one above and just about every other one I'm seeing for sale. Have I got this all wrong?

Thanks for reading, and for any input you might have.

 

[CaptainGizmo]

Hello,

Yes, you are a bit corfussled...and you may kick yourself after getting straightened out; since it's quite easy.

First off...the STANDARD on modern TOADS is to have a 6-way plug...and YES, that plug has MALE pins. That's why the coiled cable has FEMALE PINS; to plug into that 6 way! The plug on the 7-way side is also supposed to be female as the coach's outlet has male pins. This is to protect the male pins from damage; imagine the abuse they'd take if they were on the coiled cable...constantly being dropped, dragged, and stuffed into a storage box!

A 6-way is the best way to go since you'll use the standard CENTER PIN for the 12v chargeline. And, I recommend using the BEST units for that purpose since they have the functions/features needed to fully protect the newest vehicles with AGM batteries. The Blue Ox is the sweet spot for the price point and I've got a handful of my contacts using it now. I'll give you the link:

https://www.amazon.com/dp/B0DZ95DMLW?tag=rvf01-20

Frankly, your harness is what has you confused. All that mess and 4-way flats needs to be cut out of the picture and all wires connected directly on a SIMPLE 6-way outlet for the toad. You'll have all the wires directly connects via screw terminals and have full control of wire colors, simplicity, and getting everything sealed up nicely.

In case you've not got one, here is the industry-standard wiring for the 6-way...

As for the 12v source on the coach's 7-way, that will be on the 1 o'clock pin AS YOU ARE LOOKING AT THE COACH'S OUTLET.

HTH...let us know.

 

[DeltaNu1142]

the STANDARD on modern TOADS is to have a 6-way plug...and YES, that plug has MALE pins. That's why the coiled cable has FEMALE PINS; to plug into that 6 way!

Thank you... so... one of these at the front of the Jeep, no?

What confused me is that everywhere I look, this is called "vehicle-side," and the part with the female pins that connects to it is called, "trailer-side." That seems backwards to me.

Above for the front bumper of the Jeep is what I have in mind, anyway. And, as for the term TOADS, I've seen it referenced for towed vehicles but I had to do a search to see if it actually stood for anything. I guess it's the word used just because it sounds like towed, eh?

Frankly, your harness is what has you confused. All that mess and 4-way flats needs to be cut out of the picture and all wires connected directly on a SIMPLE 6-way outlet for the toad.

Yes, I agree that the 4-pin is completely unnecessary. However, I'm keeping it in the circuit for the sake of flexibility. If for some reason I end up having to tow with a vehicle that only has a 4-pin plug, then it'll be easy to make the switch.

I already have an SAE battery tender plug on the Jeep. I'm going to add the other gender SAE to the 6-pin pigtail for aux power to the, ahem, TOAD.

 

[CaptainGizmo]

Thank you... so... one of these at the front of the Jeep, no?

View attachment 32528

Yes, that is the correct outlet for the TOAD!

What confused me is that everywhere I look, this is called "vehicle-side," and the part with the female pins that connects to it is called, "trailer-side." That seems backwards to me.

Well yes, people HAVE managed to muddy the waters with mixed terminology, so I'm with you there! I've had to straighten out even some of the "pros" you'd expect to know. It's also hard when you're dealing with a hitch installer who thinks in terms of pulling a trailer rather than a TOAD.

Above for the front bumper of the Jeep is what I have in mind, anyway. And, as for the term TOADS, I've seen it referenced for towed vehicles but I had to do a search to see if it actually stood for anything. I guess it's the word used just because it sounds like towed, eh?

Yes, the term "TOAD" is just how we pronounced your "towed" vehicle.

Yes, I agree that the 4-pin is completely unnecessary. However, I'm keeping it in the circuit for the sake of flexibility. If for some reason I end up having to tow with a vehicle that only has a 4-pin plug, then it'll be easy to make the switch.

Well, honestly, like I mention...I'm not seeing anyone come up with a good reason to use a 4-way flat on the newer vehicles.

I already have an SAE battery tender plug on the Jeep. I'm going to add the other gender SAE to the 6-pin pigtail for aux power to the, ahem, TOAD.

Ok, but I must caution you have something that will guarantee you a headache at the least, and a dead battery. In the "charge-line", it is IMPERATIVE to have reverse-current protection. In the past, this was handled with a simple diode inline. This keeps/protects the current flowing in the right direction; from the coach to the TOAD...and NOT the other way. Not having this protection will cause the TOAD's battery to backfeed into the coach should the coach's chassis batteries become lower in voltage...NOT GOOD!

And, with the AGM battery, it is now common knowledge in the service industry that those give off very "dirty" power when stressed even a little. Ford's are HIGHLY PRONE to coming out of Neutral Tow mode as a result of this phenomenon!!! As you tow, the modern vehicles have too much parasitic battery draw. This a whole nuther topic, but I will emphasize the importance of spending the $100 for the proper charge-line unit that has the needed protection including the PVM filtering that keep these AGM batteries happy. You'll have the peace of low/high voltage cut-off to further protect your charging, and a diagnostic LED to let you know the status and that all is working.

 

[DeltaNu1142]

Ahhh, thanks--I have diodes in the lighting circuits, but I guess I just counted on the tow vehicle's electrical system being at a higher voltage (by way of a spinning alternator) than the TOAD's. I will look into a diode/controller for the aux power line as well.

I did start looking into flat-towing my 4WD F150--though, I doubt I'll ever need to--and some of the stories about them dropping out of flat-tow-mode due to voltage issues were eye-opening, at the least.