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Sep 15, 2004 | 07:02 PM

matt f350

Thread Starter

5th Wheeling

Joined: Jan 2003

Posts: 47

Likes: 0

From: Oregon Coast

Hot Wire

I need to hook up the 12 volt wire to the 7 way trailer plug on my 1989 F350 so it will charge the RV battery when I am towing. Should I hook the wire to the hot side of the solenoid which would make it Hot with the key off or should it be hooked in with a relay? If so how is the relay hooked up and to what? Also what size of fuse should I use?
Thanks
Matt

Sep 15, 2004 | 11:44 PM

SoCalDesertRider

Postmaster

Joined: Dec 2002

Posts: 3,959

Likes: 9

From: USA

Sure, you can go off the solenoid or the battery and use a 30 amp breaker immediately after it and a 10 gauge wire back to the plug. A cutoff switch is also a good thing to have.

Sep 16, 2004 | 09:45 AM

matt f350

Thread Starter

5th Wheeling

Joined: Jan 2003

Posts: 47

Likes: 0

From: Oregon Coast

For a cutoff, do you just mean a switch to shut off the power when not in use

.
Thanks
Matt

Sep 16, 2004 | 11:00 AM

jimandmandy

Post Fiend

Joined: Jun 2001

Posts: 5,228

Likes: 5

From: Running Springs CA

The factory tow package uses a relay, 30 amp fuse and #12 wire. The reason you can use #12 instead of #10, like in residential wiring, is because the wire is not enclosed in conduit, which holds in the heat. If you do not use a relay or battery isolator you can run down your starting battery.

Jim

Sep 16, 2004 | 02:23 PM

Toyman

FTE Chapter Leader

Joined: Feb 2004

Posts: 14,904

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From: Wayland, MI

If you start your wiring from the switched side of the solenoid you would already be doing the same thing as putting a switch in-line. The breaker is very important so you don't get any back feed surges to your vehicle.

Toyman