I’m working on my nephews 2000 F250 7.3 diesel. The brake light bulbs have been burning out for a couple weeks. The wiring and grounds look good. I’m getting 14.2 volts at the brake light socket. Would the voltage regulator cause this?

 

Check what you are getting closer to the alternator and at the battery. Usually by the time you get back to the taillights it's a little less than 14.2 volts. Normally you will read around 14.5 volts at the alternator and the battery with the engine running. If you are 15v or higher, yes something is up with the alternator or the wiring connections to the alternator.