Hello, I currently own a 98 F150 4.2 liter 2wd. My brake lights, interior lights and running lights do not turn on when I turn the light dial switch. However when I signal, the entire interior and exterior lights come on in sequence with the flashers. This makes it look like my emergency lights are on when I'm only signaling. But when I put my foot on the brake, it dims the lights and freezes the turn signals until I let off the brake. However when I put on the brake (without signaling) the running lights and interior lights turn on and stay on until I let off the brake. Lastly when I am in cruise control it shuts off once I put on my signal lights. Any ideas on what it could be?

 

You have a "bad" ground circuit.

Remove the front kick panels and inspect for body rot and loose or corroded grounding studs and connections.

 

the turn signals and brakes use the same filament in the bulb... thats why sometimes it flashes and sometimes stable... The POWER is looking for a good ground and can not find one so it is going thru the other filaments.... as SHO89 said, you have a bad ground.