The operational details of how Ford’s “smart” 7-pin trailer connector has been topic of frustration — to put it politely — for several years. I’ve criticized Ford on this forum for their lack of complete, correct, and clear instructions in the OM.

Well, last night I found this note in the 2019 SuperDuty OM:





I’ve not been able to find this note — or one anything at all like it — in my 2017 OM.

I decided to try out Ford’s instructions earlier today. Here’s the resting voltage of the fully charged AGM camper battery:






Here’s the camper battery voltage after activating the 7-pin connector’s +12V battery charging circuit and increasing the engine idle speed (see Note #2 below):





Some notes:

1) I tried to activate the +12 circuit without a camper battery attached, and nothing happened. I was able to activate the +12 circuit after I attached a camper battery.

2) With the gas engine idling, the indicated trailer battery voltage only increased from 12.8V to 12.9V. Considering the battery was fully charged and there were no +12 trailer loads, that suggests to me that there was not much charging current available at low engine rpm, even from the XXHD 240 A alternator (more on that later). However, increasing the engine speed to ~1200 rpm increased the battery voltage to the indicated 14.73 V.

We may be finally onto something about how this feature “works”, albeit it’s a tad late, and I’m not sure the instructions are complete.

HTH, and safe travels!
Jim / crewzer

 

So what's up with the trucks that owners report that the door has to be closed? That isn't how mine works, but there are some strange outliers being reported.

It's a rhetorical question, no answer needed. I'm going to say that it's a software problem, somewhere between the steering wheel and the seat.

 

I plugged in a dummy test 7pin plug and tested when the 12v charging was activated on my 2018. The dummy test plug was used to mimic having a trailer attached. I had to start the truck and put it in gear or just press and hold the brake peddle for 5 seconds to activate the 12v charging. As soon as I opened my drivers door,
the 12v charging light went out. Closed the door and all worked again.

I did the above because I was trying to figure out why my left turn signal was reporting as not functioning. Turned out I just needed to clean the plug. The plug wasn’t very dirty.

 

Great follow up question. Our 2019 gas truck’s driver’s door was open during the entire experiment with no apparent ill effect. I also did not need to select the transmission out of neutral. However, with my wife’s assistance, we did need to increase the engine speed above idle in order to significantly move the DVM’s “needle”.

I didn’t try an experiment with the camper battery disconnected and the driver’s door closed.

HTH,
Jim / crewzer

 

I found the same note in the 2018 OM:




HTH,
Jim / crewzer

 

The low charge voltage available when the engine is idling (~650 rpm?) is probably due to the alternator’s limited output at ~2,000 rpm (2.95:1 pulley ratio):


Ford addressed a related issue in SVE Bulletin Q-288:

https://madocumentupload.marketingas...968ae&v5=False

HTH,
Jim / crewzer

 

As I recall, I saw 14v+ at idle, but I have the 6.7L, not the 6.2L. Maybe the truck idled up? I don't know. I wasn't in the truck when I checked the voltage.

 

Considering the steep output vs alternator rpm curves, I suspect a small change in low engine rpms can have a significant effect on alternator output. I also didn’t check truck electrical loads (i.e., how many exterior incandescent lights were on).

The 6.7 appears to generally use higher ratio alternator pulleys (3.09) vs the 6.2 (2.95).

Safe travels!
Jim / crewzer

 

I have both sets connectors . one set at the hitch and one set at the left side wall in bed. both factory installed.

so basically, per the above, you cant use the 12v when the vehicle is off .

so I need to run some power (line from starter hot to charge controller then setup a rear battery using a take off ambulance battery box.

 

You can also convert the 7 way to always hot if so desired.

 

I was recording voltage at and current from our truck’s 7-pin trailer connector today. It would only provide voltage when the driver door was closed. Opening the driver door interrupted the circuit, and closing the door restored +12 at the connector.

Very frustrating...
Jim / crewzer

 

There does seem to be more to it than just the brakes applied.
Mine SEEMS to need to be in gear, but it slso might be the drivers door was open.
I do hope there is a software update at some time for this.
Why can't it just power up 5 seconds after it senses a trailer?