Has anyone figured out how to upgrade the charging circuit to the trailer? I think that the wire is too small, as the refer in the travel trailer doesn't work very well on dc. My old 150 had a #10 wire from the battery to the plug. Which worked fine, but you had to remember to unplug it for fear of running down the starting battery. The new '06 150 has a relay to cut the power to the trailer when the ignition is off. I'd like to retain that feature.

 

Why do you need to upgrade it? Are you going to run something that pulls more amperage than the factory rated fuse?

 

From my experience none of the reefers work very well on DC. But I guess it depends on the reefer. Are you asking how to defeat the relay so it does not shut off the trailer charge? It can be done a couple ways but not sure why you would want to risk having a dead battery in your truck. They are still 10ga wire and fused at 40 amps. Leaving it on without your truck running would be about the same as leaving your headlights on all the time. You could however just buy a GM they are still hard wired to the main bus which to me is dumb because you have to remember to unplug your trailer or keep road service on speed dial. OK now you know my opinion here is a answer.

Locate the relay in the under hood power center pull the relay and with a test light locate the pin that is powered by the ignition switch. Un clip the power center and flip it over to access the wires attached to that pin. Install a switch in the truck and wire it to that wire now you can turn the relay on and off from a switch. If you want to do it you could use diodes to isolate and have the ignition still do it and the switch as well when the truck is not running. Hope that helps.

 

In case I read that wrong and you want more amperage back to the trailer than my first question would be are you blowing the 40 amp fuse under the hood? If the answer is no than are you getting full voltage to the trailer? If the answer to that is no your not getting full voltage to the trailer and not blowing fuses than you have a bad connection in the frame harness. In some of the trailer tow packages there is a stub out harness and connection near the front of the box on the drivers side frame rail. Check your voltage there if the voltage is good there move back to the same frame rail near the spare tire you should see a multi pin connector on the that is the end of the main harness. The rear harness plugs into that check your voltage there look for green connections. There are several rear harness's depending on options but the rear harness is your tail lights and trailer wiring not all rear harness's even have trailer charge and trailer brakes. The final location or first if you start at the back is the factory 7 way connector has a connection on the back side that unplugs so you can change the 7 way if it were damaged the pins could be corroded there as well. Good Luck

 

1mainiac,
Thanks for the input. So, is that a confirmation that the factory tow package has a #10 wire going back to the plug?

 

Every Ford Truck I have seen with factory tow has a 40 amp circuit to the plug for battery charge. Even trucks without the tow package have the circuit it just ends at the rear harness. There are several rear harness configurations they all plug into the same connector. All the interior harness's have the hookup for the brake controller. All the fuse boxes have the locations for the towing fuses and relays. So electrically the only difference is the rear harness and installing the fuses and relays to make the max tow package. As to the exact wire size and length that is up to Fords Engineers but it is factory rated for 40 amps which should be more than enough to run a trailer battery charge circuit.

 

As to your reefer what make and model reefer is it perhaps I can help with that problem since it is what I do for a living. There are not a lot of 3 way reefers sold anymore and most are small units for pop ups and pickup campers. Another thing is none of the ones I know of actually cool very well what they do is maintain temp.