Troubleshooting No Trailer Lights with 2006 Ford Super Duty Pickup

Updated 07/01/2019 | Published 06/28/2019

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Question:

Ok...like above only I am getting NO power to anything at all. The trailer brake assist does register a trailer when the pin connector is installed but I dont get running lights, brake lights, tail lights, or signals. Is there a master fuse for the entire system??

asked by: Patrick

Expert Reply:

On a vehicle such as your 2006 Ford Super-Duty pickup there will be multiple fuses and/or relays for the various lighting and power circuits for a trailer. I checked an online edition of the owner's manual and the following fuse locations related to trailer lighting are noted starting on page 210. Some are in the passenger compartment fuse box; others are in the engine compartment box. Check your printed manual or the legend on the cover of the fuse box to confirm the fuse locations related to trailer lighting.

Fuse/Relay Value Function
38 20A Trailer tow park lamps
107 20A Trailer tow battery charge
301 Full ISO relay Trailer tow battery charge
9 20A Trailer tow turn signals

It is very easy to directly test the trailer (without using the truck's trailer wiring) by simply connecting a charged battery to the terminals on the trailer plug. Connect the battery negative to the plug's ground contact and then one at a time connect the battery + terminal to each of the circuits shown in the photo. If the lights do not function with direct power input then the issue is probably on the trailer. If the lights work with direct power input then you know to check the fuses and relays listed in your owner's manual.

If you have a circuit tester like # PTW2992 then once you have installed/replaced any bad fuses or relays you can test the connector on the truck to see if the signals are present.

expert reply by: Adam R