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gman69 03-26-2012 07:40 PM

Trailer wiring
 
I have a new 2012 Thor coach on a Ford chassis. Found the trailer brake harness under the dash, and got the brake controller hooked up. All the lights work. Only question is the 12 volt supply to the trailer (i use it for the interior lights in my enclosed trailer). Looks like Ford has the wire attached to the trailer connector, but apparently not connected to a 12 volt source. Anyone know where the wire ends up in the vicinity of the cab and where the 12 source is?

Full.Monte 03-27-2012 07:02 AM

First thing I would do is try to trace that wire from where it is hooked in to the trailer plug to its origin. If you can't do that, you might get lucky by looking up near the battery for the other end of the wire. You might also look at your fuse panels in the engine compartment and see if there are any wires connected to one side of any fuse, but not to the other. Also, look for missing or burned out fuses. There should also be an isolator--looks like a 2 inch cubical part with wires attached that isolates the engine battery from the trailer battery, so you can't draw down the engine battery by using any electrics in the trailer.
As a last resort, you could run a new wire from the + side of the battery through an inline fuse all the way back to the trailer plug. Remember, though...you may draw down your engine battery doing this.

chuckinthebus 03-27-2012 07:33 AM

Have you tried your volt meter to see if there is one wire in the coach plug that has 12v continuous? Not sure on moho chassis, but all pickups and vans I have owned over the years, should be a yellow wire (if memory is still ok) that should be hot.

Hikerdogs 03-27-2012 09:33 AM

Quote:

Originally Posted by gman69 (Post 1126188)
I have a new 2012 Thor coach on a Ford chassis. Found the trailer brake harness under the dash, and got the brake controller hooked up. All the lights work. Only question is the 12 volt supply to the trailer (i use it for the interior lights in my enclosed trailer). Looks like Ford has the wire attached to the trailer connector, but apparently not connected to a 12 volt source. Anyone know where the wire ends up in the vicinity of the cab and where the 12 source is?

Ford does not connect any wires to the trailer hitch socket. The wiring harness supplied on the incomplete chassis to the body builders extends only to the rear of the drivers side frame member. All the wire ends are taped and folded back into the harness. The body builder decides what type of trailer socket (4 pin, 6 pin, or 7 pin) to install, and which wires will be terminated in the socket.

If all the wires are not terminated follow the harness from the socket back to the outside rear of original drivers side frame member (not the extensions added by the body builder). The remaining wires will be folded back and taped inside the harness.

camper33 04-07-2012 06:29 PM

The 12volt on a Ford is only on when the ignition is turned on. The fuse for that lead, which is usually orange is located in the fuse panel located under the hood.

garykk 05-22-2012 11:03 AM

Quote:

Originally Posted by camper33 (Post 1137284)
The 12volt on a Ford is only on when the ignition is turned on. The fuse for that lead, which is usually orange is located in the fuse panel located under the hood.

I am assuming that Winnebago put the 7 pin connector at the rear of my MH. My question.... is the 12 volt supplied protected from back feed in the Ford part of the chassis? I know the Chev truck TV I had was and when connected to the 5th wheel ,charged the 5th wheel batteries. Reason for asking is that I want to charge the toad battery which will be running the brake system. Either that or I need to figure out how to switch the keyed 12 volt to battery 12 volt in the Ford chassis..

camper33 05-23-2012 04:27 AM

I don't quite know what you mean by protected from "back feed". The current will flow both directions, if the toad battery is low the current will flow to it. If the tow tow vehicle battery is low the current will flow to it from the toad. The Ford chassis will Isolate the batteries when the key is off. The GMC products and Dodge have a constant 12volt at the 7 way plug.

garykk 05-23-2012 11:44 AM

I was wondering if Ford had a diode in the line to prevent 12 volts from flowing back into the coach......

camper33 05-24-2012 04:28 AM

If your engine is running then the chassis is producing more current and voltage than the battery in your toad or trailer, and when you shut off the ignition the relay drops out separating the to batteries, therefore no need for a diode.

Towertime 05-28-2012 10:17 AM

When I added the brake controller to my 2012 Thor ACE, (2011 F-53 chassis), I found a wire stowed and marked (dome) near the right rear of the RV underneath. I had to remove some of the protective plastic to find the blue wire for electric brakes and was also looking for a 12v wiring source. The dome wire is switched through the dash lights dimmer. Turn them full bright until it clicks and the 12 volts is present. You don't need the keyswitch or lights on, just the dimmer switch in the "clicked" position.

Towertime 05-28-2012 08:10 PM

By right hand side, I meant the passenger side near the back...within a couple of feet of the hitch.

gman69 06-07-2012 04:33 PM

Got to checking, and the trailer feed wire is hot when the key in the ignition is ON or in the aux position. I would like to have the feed wire "hot" all the time, so that power is available in my cargo trailer (interior lights). Tracked the wire to the "hood" area of the motorhome, but lost it in the maze of wires there. Anyone found the wire and where does it go (to one of the fuze panels?)

Again, the coach is on a 2012 ford 53 chassis with a V-10.

Towertime 06-08-2012 08:04 PM

I don't know if you looked for it , but the wire I was talking about would probabably do what you want. I am using it to keep my breakaway system charged up on my tow dolly, but I think you could use it to run lights in a trailer. All you would have to do is put the instrument panel lights switch in the full bright position (where it clicks to turn on a dome light). Since my Thor F-53 doesn't have a dome light in it for the cockpit, it becomes just a switch for 12v for the dome light wire, which I found just a couple of feet back from my receiver hitch. The 12 volts is there even when the ignition switch is off as long as the intrument panel light switch is in the full bright "clicked" position.


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