What amp fuse for charging circuit from truck Alt?

[Arktikos]

I have a new (to me) 2006 Chevy 2500 and a camper to go with it. This truck has a factory tow package but the red wire "battery feed" on the factory plug at the bumper is dead, even with the truck running. Instead of trying to track down where that red wire goes under the hood I want to run another wire from the truck battery back to the camper and was wondering what amp fuse I should use to protect this circuit?

I am ordering this isolator switch Smart Dual Battery isolator which is rated for 140 Amp. Was thinking about a 200 amp fuse so that it wont blow when there is a low battery condition in the camper, coupled with say, lights and the DC fridge running starts drawing a lot of amps from the alternator.
Thanks for any advice!

[time2roll]

If you must pull wire I would just use simple #6 wire and 60 amp fuse holder.

http://www.genuinedealz.com/maxi-fuse-inline-fuse-holder-w-6-awg-leads-up-to-60a

Honestly I would have the oem circuit fixed. Might be just a new fuse.

Either way consider 100 to 200 watts of solar on the TC to charge the battery. To rely mostly on the alternator is probably setting you up for disappointment.

[Arktikos]

Thanks so much! this info you have given has been so valuable to me. I opened up the fuse box under the hood (Nice I didn't have to stand on my head to look under the dash!) and found where Stud#1 is. Appears to be just a red piece of plastic plugged into it. Am heading to NAPA now to get a 40A.. Maybe we'll have power to the camper for the trip we got planned for Monday! If so I wont bother running another wire back to the camper as I just want the batt back there to charge up after a day's driving. Not really needing a lot of power for this little 8' cabover..
Thanks again.

[Golden_HVAC]

Hi,

If you have #4 wire going all the way to the trailer, then a 100 amp fuse is the max size that should be used. You will not get more than 50 amps to travel between the two 12 volt batteries. You will need a very oversized connector, like a forklift battery connector to get more than a few amps from the truck to the trailer. Look for a 50 amp rated 'anderson connector'. It will handle 75 amps without getting warm, and is rated at 50 amps when plugging in and out all the time without a problem.

The wires going through the factory wiring harness are probably #12 wire - rated around 20 amps, and with that distance, probably will never see more than about 10 amps going into the trailer battery.

By connecting a wire directly to the alternator, you will get a full 14.2 volts, while the battery probably only has about 13.5 volts.

Good luck,

Fred.

[wolfe10]

Fuses are sized to protect the WIRE, so the wire gauge will determine the correct fuse.

It will be in the range of 10-30 amp depending on wire gauge It will be in the line from isolator (right at the isolator)to the camper.

Be sure to run a comparable gauge ground/negative wire from camper to truck frame.

[wnjj]

The under-hood fusebox has a fuse called stud#1. It's 40A and feeds the trailer plug. There's no isolator other than pulling that fuse.

If you run your own wire, the fuse should be sized to prevent overloading that wire.

If you want to add an isolator to the existing wire, it's connected to a post (stud) just outside the fusebox and you can put the isolator in series there.

[Bob_Olallawa]

Take a look at the owners manual if it is still with the truck. Should be a place in the large under hood fuse box for a fuse to protect that line. Maybe the old owner never plugged one into it.