No interior lights in enclosed trailer

My daughter has a 2006 Tacoma with the factory tow package, and uses an enclosed trailer for her business, the interior lights in the trailer don't work, and the brake controller says there is no trailer connected.

My ford-150 had a fuse that the factory leaves out (probably for liability reasons) that had to be put in, in order for the interior lights on this trailer to work on my truck (haven't tried the brake controller on my truck yet).

I am wondering if there is a fuse that has to be installed on the Tacoma to get the lights and controller to work? If there is where is it located and what amp is it, I looked in her manual but didn't find anything about it. My Ford manual didn't mention a fuse either, I wound up taking my truck and the trailer to the dealer she bought the trailer from and they put the fuse in.

 

Does the trailer use a 4 pin plug or the 7 pin? On mine (4 pin) you have to have the parking lights on to use them. Mine has a switch to turn them on and it gets it's power from the parking lights on the trailer.

Does the trailer actually have brakes on the axle? That could be why the controller isn't showing anything or if using the 7 to 4 pin adapter it would probably show the same.

 

Did you check for continuity on the bulb?

 

There is a relay in the fuse box under the hood. Check to make sure it is actally there. Its location is marked on the inside of the fuse box lid.

 

The plug is the round 7 pin plug, not the flat 4 plug. Yes the trailer has brakes , there is a battery on the hitch with emergency break away cable that actuated the brakes if the trailer ever came loose.

 

Check the lights with the ignition on. There won't be 12v power to the plug with the engine off.

 

In my experience with my boat trailers is that 9/10 times its a grounding problem. My parents horse trailer had a grounding problem and none of the lights worked.

 

If the trailer has a battery it should light the lights unless it a little one just for the breaks. The trailer plug 12 volt charge feed will not work unless the key in the truck is on to keep the truck battery isolated from the camper battery while it's not running. If you have the factory set up it should have 12 volts at pin 4 only with the key on. If you are looking at the truck trailer connector it will be at 1:00 o'clock

 

Thanks for the help I will check for power on pin 4 and check to be sure the relay is in the fuse box. It maybe a couple weeks before I can do it she is taking the truck on vacation. I will let you know how I make out.

 

My cargo trailer's interior light will not light unless the headlights on the truck are on while plugged into the truck. Pretty much useless.

 

Finally got a chance to check the pug on the truck, there is power on pin 4. I am going to run a jumper wire between pin 4 on the truck and the trailer plug, and another for the ground and see if I get interior lights that way. if I do that will mean loose connection within the plug, probably on the truck side.

 

i just found out that the trailer interior lights won't work unless the truck is running.

I'm stumped by the controller, I bought the direct plug in cable from Tekshonka it has 2 white ground wires at the controller plug, one goes to the plug on the other end of the cable which plugs into the factory brake controller plug on the truck, the other white wire has a ring connector and grounds to the truck with a bolt. I never connected that wire with the ring connector because I figured the unit was grounded through the other wire. I grounded the ring connector today and the controller still says no trailer connected. I used a set of small needle nose pliers and squeezed all the contacts in the trailer plug to be sure they were making connection when i plugged it into the truck, that made no difference. I put a jumper wire between the brake connections and another between the ground connections and that didn't make a difference either. I guess I will just take it to the place where she bought the trailer and have them get it working, because they may have to adjust the trailer brakes themselves.