'90 Ford E350-Headlights Keep Burning Out

Driving down road last night, headlights go out. Switched to bright, they came on. Drive around parking lot, brights go out, too. Checked all fuses. Looked OK. Drove to Checker Auto Parts, bought two new headlights. Worked for about 20 miles. Brights were on, then go out. Switch to dims. Dims stayed on for the next few miles home. Haven't driven again, but assume these will go out as well, soon! All turn signals, interior lights, brake lights, everything else, works. I'm a woman, and I'm not real electrically inclined. Not a whole lot of money to take to a repair shop. Can someone help?

Are the lights are burning out? Do they get very bright before they cease to function? Could be an overvoltage problem. Use a voltmeter and check the charging voltage to the battery. If the voltage is too high, the voltage regulator is defective. If the voltage is okay, then it could be a defective high/low switch, but that wouldn't cause the lights to burn-out. We need more information to give you an accurate answer.

IF Bulbs are burning out,overvoltage is likely problem,,but if bulbs are ok ( and I feel they may be)
Problem seems that it Should be Dimmer switch or wire harness connection (on floor under carpet or rubber mat)

Have a Great Day,, Steve