B-Rye

On the truck side of the 7 blade trailer towing electrical plug, can the hot lead from the plug for trailer battery charging be spliced into any hot wire on the truck near the bumper or should a wire be run all the way to the truck battery? What amp fuse should be placed between battery/hot wire and truck side plug?
Thanks

old_programmer

You should run the wire from the battery. I used 10 gauge on my last two vehicles but with this recent one I wish I had run 8 gauge for the extra load capacity I'll be needing in the near future. I installed a 40 amp breaker near the battery. I also installed a relay that piggybacked on a circuit that is switched with the ignition. Without this you would need to disconnect the 7-pin when you stop to prevent draining of the tow vehicle starting battery.

Here are some links to the types I used:

https://www.amazon.com/Bussmann-BP-C...ircuit+breaker

https://www.amazon.com/TE-BOSCH-Curr...ds=bosch+relay

I used something similar to this. I don't remember the exact one but you should be able to find something to fit you vehicle.

https://www.amazon.com/Circuit-ATC-P...ve+fuse+holder

B-Rye

Thank you for the info. This will help alot!

rjniles

If you have a newer truck with a tow package, the wire to provide power to the 7 pin is in place. You need to add a relay and fuse in the under hood fuse panel. The owners manual calls for a 20 amp fuse.

RA013023

Another thread, same question today. By coincidence, I just happened to have the box for the relay I installed, sitting here. Here's the NAPA part for the Relay.

B-Rye

Thanks for the info, that will help. I am not too experienced though with wiring..how do I hook this all up? Truck battery- relay- fuse- plug at back of truck in that order?

PerryB

What year is the truck, and did it come with a 7-pin plug from the factory? If it did, all you have to do is install a fuse and a relay in the fuse/power distribution box.

larry2c

Interesting thread - I had assumed that with the "trailer towing package" the 12V lead would have been done at the factory. Is it fairly obvious when you open up the fuse box where the lead is to put the relay in place? It's dark & raining so I'm not venturing out to check right now...

B-Rye

Perry B...2008, it did not come with the 7 blade plug. Bought the truck used and it had a 4 prong on it. Hooked the lighting part from the 4 prong to the wires for the 7 plug that I got @ Walmart, now trying to make the connection for the trailer battery charging.

rjniles

You need to look at the diagram in your owners manual. The box only shows the fuse and relay position numbers.