Hi everyone,
sorry in advance if these issues have been solved on the forums before but I'm short time to browse archives.

So I have tested my 7-prong bumper plug and found no 12V hot wire. All is dead with lights off/ key off.

Turn headlights on and still no hot terminals. (I would expect one for trailer running lights, right?)

Turn key on (with lights off) and I've got 2 hot terminals. Truck has an electric brake controller, so am I to assume that one hot is the brake controller...(but wouldn't it only be hot when the brake pedal is pushed?) and the other is the 12V hot?

Fuses all look good.

With signals on I can find right and left turn blinker terminals no problem. (so I know I have a good ground)

There's also a midship wire that comes off the main trunk, presumably for camper lights / sled deck lights, what have you. What I'm actually wanting to do is tie into that and wire a 12V hot + running lights +ground to connect to the front of my camper for lights/running lights/fan/radio etc. in the camper.

Any suggestions as to why there'd be hot wires with the key on but no hot wire anywhere with the key off? Also, any suggestions on how best/easiest to achieve what I'm after with my camper wiring would be appreciated : )

Scotty

 

There are no wires that should be hot with the key off except the marker lights if they are turned on. When the key is on there is power continually to one point designed to charge an emergency breakaway battery on a trailer, or operate accessories while the truck is running. The electric brakes should only be hot when the brakes are applied unless you have a failing brake controller. The alternate possibility is that you have had somebody rewire the trailer electial and its wrong. (happens more often than you think) If you get under the truck near the rear bumper ont the driver side by the crossmeber and frame rail the wrirring comes up and has a couple of connectors to the main harness for trailer electrical (assuming you have the factory towing option) these connectors sometimes get loose break the tabs off etc. make sure they are plugged in good, and check your wire colors and diagram on your connector to determine they are wired in the correct postions. The if nessasary temporarily disconnect your eletric brake controler and see if you still have 2 continually hot points as you can tell if thats your problem there.

 

Just looked @ my FOMOCO 7 pin connector (pn F4TB-14A464-AT)it has (not in any order) [1] + (hot ignition on) [2] - (ground all the time) [3] parking/running lights (hot w/ lights on) [4] left brake/turn (hot w/ L brake/turn on) [5] right brake/turn (hot w/ R brake/turn on) [6] electric brake (hot w/ brakes {if brake controller hooked up} or 4 way flasher) [7] reverse (hot in reverse). Agree w/ oversize w/ key off & everything else off nothing is hot. Activate any of the above & it s/b hot.
Check all of your fuses and your connectors under bumper. You may have to zip tye your connectors together if their retainers are missing or they won't stay together/connected. Draw a picture of the connector on a full sheet of paper and w/ a test light check each wire and lable it on your drawing. Check against your trailer connector if it does not match up start tracing wires under the truck to see where someone messed w/ it.

 

Thanks Brain and Oversize for your suggestions. Shall check that out. Failing brake controller seems possible, as the red light on the controller itself is not always steady when brakes are on (flickers). P/O tells me that hooking the truck up to a 'standard' trailer 7-prong resulted in all the lights and brakes etc. working correctly. Still need to figure out the lack of hot wire when lights are on.

So as kind of an aside... what do people do for campers that don't have batteries (so need hot wire all the time for interior lights)... just run a hot wire from the engine compartment somewhere?

thanks again,
Scotty

 

check your fuses in the box under the hood. make sure there all good.

and i belive all campers have there own battery that charges off the aux plug. if yours dosent i would look at putting one in if you hardwired into your truck you might go to start the truck and have dead battery.

 

Travel trailers usually plug in to 110 Volt AC at the point of use. They also usually have a 110V AC to 12 V DC converter built into the trailer for it's lights. IF the travel trailer has a battery it may or may not have electric brakes BUT it will have a hot from the towed vehicle to the trailer's battery to charge the trailer battery while you tow. It will also have a hot from the converter to the battery so when it's plugged in it charges the battery, and when it's not plugged in the battery runs the 12V items (lights, heater & fridge ignition, water pump, etc).
Find your owners manual and trace your fuses. There is I believe a main (MAXI) trailer harness fuse and specific (STANDARD) trailer harness fuses. Make sure you pull them out and check each one.
Lastly climb under and look for ANY damage or "improvements" someone may have made to the harness.