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Late Model Ford Truck and Camper Battery Charging

ford battery charging

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#1 kielhwl



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Posted 15 May 2018 - 01:19 AM

Our new Ford F350 won’t charge the truck camper battery! Has anyone heard of any problems with late model Ford trucks not sending power back through the trailer hitch’s seven-pin connector to charge the truck camper’s house battery? I’m pretty sure it isn’t my Truck Camper, but is something in the logic Ford uses to decide to send current back to charge trailer or TC house batteries. I’m also sure it isn’t the common problem most trucks have of too small of a wire to get enough current to the TC battery. NO current is making it back to the the trailer hitch 7-pin connector.  Also, the electric brake controller and truck’s logic display on the dash panel’s display indicate nothing is connected to the trailer hitch 7-pin connector. 


Here is some geeky technical trouble-shooting background: 


-We got a new 2017 Ford F350 for our older truck camper. According to our Victron battery monitor, our old Tundra could get about 1- 2 amps back to the TC house battery. Our new Ford couldn’t get any current from day one.  


-I’m pretty sure the problem isn’t with the TC. I started trouble shooting the TC wiring, and determined that the TC’s house batteries voltage could be measured from the TC’s pigtail connecter when it was unplugged from the trailer hitch’s 7-pin connector. The voltage was within 0.05 volts of the battery voltage measured at the battery posts and by the Victron battery monitor. So, I’m pretty sure my TC 12 volt charging wiring is fine from the trailer hitch to the battery. 


-Then I checked for a voltage on trailer hitch 7-pin connecters’ 1 and 7 o’clock positions (as well as all the others). There was no voltage detected for battery charging but all the running lights etc. worked fine. Then I checked the fuse for the trailer-charging relay and found it missing so replaced it. There was still no current going back to the pigtail. 


-I took the truck and camper to the dealer. It turns out, not only was the fuse missing, but also the relay and its wiring harness, and fuse and relay socket for trailer charging. They ordered the parts and were about to replace them when they contacted Ford again and found out the design was changed, but not yet recorded in the tech manuals. Ford now has a new circuit system that won’t close the relay to send current back to the 7-pin connecter unless the pigtail is plugged in and “detected”. My truck was assembled in July of 2017 and we bought it in December.


-But when my pig tail is plugged in, it won’t trigger the logic to send current back to the 7-pin connecter. Nor does the truck’s integrated brake controller recognize that there is something plugged into the trailer hitch 7-pin connector.   








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#2 klahanie


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Posted 15 May 2018 - 03:59 AM

Read about similar probs over the years...


Found this bulletin




Not sure exactly what you might need to replicate a trailer plugged in (might need a certain amount of electrical resistance for eg) but I have read you might also have to apply the service brake when plugged in to turn on the sensing.


Also, if you haven't already, you could search/ask on this forum:



Good luck with it !





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#3 Riverrunner


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Posted 15 May 2018 - 04:37 PM

This is when the trucks are getting too smart...  


Some have had issues with this and with trailers with LED lights.  The LED's dont' draw enough power so the computer won't turn on the charging circuit.  This adapter may or may not help.  https://www.curtmfg.com/part/57003  


The other thing to do is to jump some wires so the 12v charging circuit is always hot like in the old days.  I have not done this yet but will.  See the attachment.  



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2017 F350 Crewcab, LB, 4x4, 6.2L 
2005 FWC Grandby



#4 Bigfoot Dave

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Posted 15 May 2018 - 05:22 PM

I had a turn signal wire short on my 2012 F350. There were no blown fuses but the turn signal would not work. One of the mechanics at the dealer said they had a similar problem on a Mustang and had to connect the computer to the vehicle and reset the problem code for the turn signal. The computer detected the short before the fuse could blow and isolated the problem circuit. I wonder if this needs to be done on your truck? Good luck, Bigfoot Dave

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#5 Machinebuilder


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Posted 15 May 2018 - 06:41 PM

I cant help on  the 2017.............

are you sure about the pins you are checking?


on my 2011 F150, aux power and ground are opposite each other, this is RV standard wiring 7 blade connector. There is a hard to read diagram on the cover plate.


I do have the trailer tow package with built in brake controller, yes the factory does not install the relay or the fuse. (there was a baggie in my glove box with them)


I think the brake controller only senses if  trailer brakes are connected, ie if you had a trailer without brakes it would still say no trailer.


my battery seems to be charging fine from the 7 pin trailer connector, according to my cheap monitor.

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#6 kielhwl



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Posted 16 May 2018 - 01:35 AM

I want to thank you all for your quick responses. I am digging in further on this topic. I agree, cars are getting too smart. 


 I may try the "jumping the circuit" as described above. I can see all the parts that are described in the PDF, but being a brand new truck, I really don't want to violate the warranty. 

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