12V power to RV 7-pin receptacle
05-02-2019, 06:36 AM
#1
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12V power to RV 7-pin receptacle
Just FYI, most might already know, couldn't find it on these forums, even a 'max-tow' truck probably doesn't have the fuse or relay installed for 12 volt power to the 7 pin RV plug receptacle at the hitch. I don't use my rear defroster so I used that 30 amp fuse and I don't have powered stepboards so I used that relay. The owner's manual for your truck will show the exact locations for the fuses and relays in the main fusebox under the engine hood. I found this out because I installed an electric jack on my camper that has a 7 pin plug to use the RV receptacle. Now I can also charge the RV battery while towing. Doubt I ever need the battery though.
05-03-2019, 01:21 PM
#2
Senior Member
What are you using to run the power to the 7-pin? The aux wire in the harness is for trickle-charge current only, like the utility batteries used to apply brakes during a break-away.
05-04-2019, 01:29 PM
#4
The 7 pin trailer tow plug provides full current to the trailer battery, it's not a trickle charge. It gets just as much juice as the trucks battery.
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05-04-2019, 03:27 PM
#5
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In the 90s, the trailer battery charge circuit is ~8ga, and was fused for 30A. Since the OP used that size fuse, I assume it's at least the same size wire on your newer trucks.
05-06-2019, 09:54 AM
#6
Senior Member
There are threads regarding the inability of the newer trucks to fully charge anything larger than small utility batteries.
05-06-2019, 10:30 AM
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05-06-2019, 07:15 PM
#8
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Fun fact: Ford's 2016 manual doesn't have the trailer power fuse listed correctly (at all) so I had to use trial-and-error...its #36.
Last edited by massspike; 05-06-2019 at 07:18 PM.
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05-07-2019, 06:08 PM
#9
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I designed & built this to prevent that exact scenario - it works.
(phone app link)
No matter what happens ON THE TRAILER, the truck fuse will not blow. It will only blow for a fault ON THE TRUCK (between the fuse & my limiter). So the trailer always receives current, even if the voltage is very low.
(phone app link)
No matter what happens ON THE TRAILER, the truck fuse will not blow. It will only blow for a fault ON THE TRUCK (between the fuse & my limiter). So the trailer always receives current, even if the voltage is very low.
