power for the 5th

[Chuck1]

I have a 94 6.5 I use for towing a 25ft 5th wheel . A friend has a d/max with his 5th If the batterys in his 5th get low he just plugs in the trailer plug and it seems to run off the truck batterys .It has the factory plug set up .With mine it won,t power it off the truck unless I use jumper to the trailer batterys . Any one know what I would have to do to make it like his.

[96ccdd]

If your 94 is anything like either on my 96's, you should have an orange wire located in the trailer harness that should be on the drives side engine compartment by the steering column which get terminated in the main power box. this wire should already be connected in you plug.Hope this helps.

[Roy W]

Chuck.....The other thing to check is that the fuse may never have been installed to activate your battery charging circuit. Go to the underhood fuse box mounted on the fender well on the drivers side. There should be a big fuse (40amp) in the upper left hand corner which controls the trailer battery circuit. The fuse in the upper right hand corner(30 amp) is for the brake control circuit. These fuses do not come from the factory installed and are usually part of the trailer towing package kit that comes in the glove box on new vehicles. I don't know what year they changed the design of the fuses, but the earlier ones used a 40 amp Maxi-Fuse and the newer ones use a 40 amp square type. I always keep an extra of both still in the package laying under the fuse box cover, just in case......

[Chuck1]

My system is charging all right when the truck is running.What I was talking about is when the truck is shut off my friend with the D/A can when he has a low battery in the trailer plug into the truck with the trailer cord and run off his truck .This is what I would like to do.

[Roy W]

When I said battery charging circuit, I meant the trailer battery charging circuit. With the truck running and the trailer plugged in to the truck (and no shore power attached), check the trailer battery voltage. If it's not at least 13.5 to 14.5, the trailer battery charging circuit in the truck has not been activiated by the installation of the 40 amp fuse. If the trailer battery IS being charged by the truck, then someone has installed a battery isolator on the truck. This is sometimes installed to keep from draining the truck battery so the point it wouldn't start if the trailer has been left plugged in and the truck not running.

[Chuck1]

I think I do have an isolator but would the D/A have one and still be able to run the trailer stock.

[Roy W]

Chuck.....The D/A doesn't come with an isolator, someone would have to have added one, and if they did, no, the trailer couldn't run off the truck. The islolator is nothing but a high capacity diode, or think of it as a one way check valve. Power to the trailer, but not the reverse. I'll be honest with you, I've been towing travel trailers for 35 years with six different trailers, and I've never installed a isolator in any of my vehicles. You just have to remember to unplug the trailer from the vehicle if you are going to leave it hitched up for any period of time. Not having an isolator has one other benefit too.......If your truck battery gets low, and your trailer is plugged into shore power, just plug the trailer into the truck, and the trailer converter will charge the truck battery...... Slowly, but it will charge it.

[Chuck1]

Roy I must have a isolator then if my truck dosnt run the trailer when the truck isn,t running. Would you know what one would look like.I gess I should un hook it.

[Roy W]

Chuck......If you're sure that the 40 amp fuse is installed, and that your truck is charging the trailer battery, then you probably do have a battery isolator installed in the truck charging system. Most battery isolators are about 3" X 5" and are finned aluminum, and mounted under the hood somewhere. It probably has 3 wires (about 12 gauge) going to it. They are mounted on small studs, and one comes from the alternator, one goes to the truck battery, and one goes to the trailer battery. To take the battery isolator out of the system, all you have to do, is remove the three wires, and fasten all three together with a small screw or bolt through the terminal eyelets. Then you have to tape it up real good and tie wrap it up and away from any metal surface, because all three of those wires are hot and you sure don't want that much current to short to ground.

Using your truck battery to power your trailer when the trailer battery is low should be limited to an emergency only. Such things like a heater fan, or a refrigerator on 12 volts can kill a truck battery pretty quick, although a two battery setup in a diesel truck will obviously last longer. Just remember to unplug the trailer from the truck when you don't need it........Roy

[Chuck1]

Roy I have a round thing that looks like a starter solenoid on the fire wall could that be it.

[Roy W]

Chuck.....Yes, that is probably it. Solenoids like that are used frequently as a battery disconnect switch. To check it out, run a jumper wire between the two big 1/4 inch posts and see if you have power to your trailer. If you do, that's it and you can take the wires off those two terminals and connect them together, or just put them all on the same terminal. Either terminal is okay, You're just using it as a binding post. If you do that, you can leave the solenoid in place in case you decide to hook it up again some day. The two (or maybe only one) small wires you can leave hooked up to the solenoid. One comes from the ignition switch, the other (if you have two) goes to ground, and they won't hurt anything if you leave them hooked up. I think you found your problem......Roy

[brypay]

This may be questioning the obvious but are you staying hooked up to your trailer for ground continuity. If you are unhooking and leaving the trailer plugged in you may not be adequately grounded.

My truck powers my 5th wheel without problems, no isolator but I do watch the power drain and start the truck every day when I'm not on shore power.