Headlgihts on 1994 F150

PERHAPS IT HAS A RELAY FOR THEM UNDER THE HOOD

sounds like a bad front control module or a bad IPM. But you need a scan tool to really diagnose it.

Change the bulb. When you press the pedal the brake switch changes the circuit to the 21w brighter circuit for the brake light.

I'd be willing to bet your dash lights don't work either when you turn the headlight on.change the headlight switch, it has a short, it's only about 11 dollars at advance auto, and is fairly easy to replace. my 93 chevy did same thing, changed headlight switch, problem solved

check your fuses under the steering columb area, and also check fuses and relays, that is located in a power distribution black box under the hood, on the drivers side.

I had the same problem. It's the blinker switch in the steering column.
You'll need to pull the steering wheel, any cheapo s/w puller will do.
Unscrew the turn signal lever from the steering column. Replace part.
Worked like a champ for me.

The first thing you have to do is get a test light. Turn your park lights on and see if you have power to the tailight. If there is power, you need to replace bulbs. If there is no power, probe the wire from the bulb socket back, until you find power. If you have an after market trailer plug on there, that s a good place to look for a short. Especially where the wires are spliced in.

Sounds like it could be the headlight switch.

When asking a question about a car, please include the details about the car. Most automotive lighting systems run the circuits powering the lights in a series, which means if one goes out, other may quit working as well. If one taillight isn't working and the other is, and you are sure it is not a taillight bulb, check the rest of the bulbs in the car, front and rear blinkers, hazards, parking lights, headlights, and brake lights. If everything else is good, about the only option left is a faulty ground connection, which you can look for visually, but usually requires a wiring diagram and a multimeter to track down.

The fuse to the taillights/running lights?
It can't be a grounding problem if both taillights and dash don't work.
If only taillights don't work, it would be suspicious grounding.