I just purchased a 1993 F-150 4x4 with a 302 engine. The headlights flicker after about 5 minutes. It seems that they will flicker more often when the bright lights are on. There are two after market fog lights that are grounded, but the hot wires are not hooked up. It seems to me that something overheats causing the lights to flicker. The dash lights don't flicker, just the headlights. Standard Sylvania 9007 lamps are being used. Is this a switch problem? Any help would be appreciated.

 

sounds to me like a bad connection. check the connections at the headlights. see if anything is corroded or loose. the natural vibration of the truck may be causing a rattling connection.

 

It's most likely the switch, for 2 reasons:
1) It has a built in circuit breaker for the headlights (same circuit used for hi & lo beams), and as it ages, it can become more sensitive
2) They're known to burn their terminals off.

Get a Haynes manual PN 36058 & read how to get to the switch and test it in the last chapter.



When you get the dash bezel off, you'll be able to see if you need an new connector, too. The dealer number for that pigtail is WPT-165, but IDK the price.

 

It's not a loose connection, because vibration has no effect on it. The lights will flicker with the truck in park just as much as bouncing down a dirt road. The switch makes much more sense.

 

I changed the light switch and the lights are working as they should now. Thanks for the help.