What could be wrong in a 1965 Ford Mustang Coupe if after the headlights have been on bright for a while they start flashing on and off but only when they are on bright?

Answer 1

You may need to replace the headlight circuit breaker. Most vehicles manufactured by the Big 3 have breakers that protect the headlight circuits. Sometimes the breakers fail and need to be replaced. If the headlights seem ok and you don't see any dimming when you go to the high beam, the problem is probably the breaker. The headlight switch itself is probably the culprit. Usually, when the high beam switch goes out, it stops working altogether. The headlight switch will cause the lights to go off intermittently. Answer The amperage draw of the headlites on high is exceeding the capacity of the headlite switch; this exact same thing happened to me when I switched to halogen lamps. Replace your existing one from a 1970 plus Mustang will fit right in and take care of the problem --- unless you like the effect.