I have a 1983 Ford F-150 with a 351w. After I let it idle and warm up, everything flickers, headlights, dash lights, taillights, etc. it only does it when it’s warm though, if I start it up and turn the lights on or whatnot, it doesn’t flicker, after about 5-10 minutes of it warming up they begin to flicker when the motor is warmed up. Any answers?

 

A good place to start is the charging system. It does sound like the alternator is being affected by a questionable voltage regulator.