Q: TAIL LIGHTS on 1999 Ford F-250 Super Duty

Rookie cbe0621eac06868b3efe0d8d1d3611e23c60d3114864ea2ec19a68cfbd3eebab
(2) Answers
Customer Concern: Intermittent but repeated blowing of fuse 8 (15 amp) in the Battery Junction Box (BJB) causing a loss of parking light function. The brake lights, turn signals, and headlights all work properly. All parking light bulbs were removed but the fuse still blows.
Tests/Procedures: 1. Disconnect the Brown (BN) wire at the C1045 connector located under the master cylinder to isolate the rear exterior lights away from the front exterior lights and cab lights. C1045 is a 16-terminal black connector.

2. If the fuse continues to blow, disconnect the BN wire at the C1049 connector and look for the fuse to stop blowing to isolate the circuit from inside the vehicle to outside the vehicle. C1049 is the top bulkhead connector on the driver side of the firewall. The BN wire is terminal 21 (circuit 14) in this connector.

3. If the fuse stops blowing when disconnecting the C1045 connector, verify that the circuit feeding the tail lights is not shorting to ground near the light sockets. Also check the trailer harness connection and the license plate lamps and circuits for a possible chafe to ground or shorted bulb filament.
Potential Causes: Shorted Circuit
Parking Lamp Bulb

I had the same problem 1989 F 250 Lariat
replaced head light switch. FIXED PROBLEM.
Not all that hard to do.