Gust got my first mustang and need some advice on the wire harness has a shortage some where when headlights are on after a few minutes they shut off push switch in and back out and they come back on any ideas
Step one is get a wiring diagram for your year. They vary by year a good bit.
The headlights are protected by a circuit breaker. If it senses an overload, it trips or opens. When it cools down, it works again. Should be in the headlight switch, although I am not familiar with an 86. You may have a worn wire shorting, or a poor ground, drawing too much current, bad connections at the lamp sockets, or the circuit breaker itself is tired.