my tail lights and license plate lights are out. all other lights work to include brake lights turn signals and reverse lights. All the fuse’s are good and have 12 to 13 volts running through them. when all the bulbs are pulled out for the license plate and the tail lights all the sockets recieve 12 to 13 volts. but as soon as one bulb is put in all the sockets drop all the voltage. i’m figuring it is a series circuit of some type i just can’t figure out why it drops all voltage as soon as anything that pulls a load is put on it.
In this case my first thoughts are to look to see if you have trailer wiring installed. factory or aftermarket. More often than not, truck tail light or brake light issues are caused by poor connection or corroded trailer wiring. My second thought would be, test the light bulbs.
Looking at the wiring diagram (see below) it looks like the tail lights and plate lights are feed from the same BROWN wire but makes a difference if you have dual rear wheels or not.I have added the wiring diagrams below to help assist you in tracing down your problem.
1) 2005 Ford F250 Super Duty Exterior Lights 1 of 3
2) 2005 Ford F250 Super Duty Exterior Lights 2 of 3
3) 2005 Ford F250 Super Duty Exterior Lights 3 of 3
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