Another suggestion is that it could be a dirty connection causing resistance at the bimetallic strip that Hotrod Lincoln references. This happened to me and there was no short, just needed to clean the points at the connection. What happens is that the dirty connection gets hot with a normal current draw, as you would have with the headlights on, and the heat causes the bimetallic strip to open the circuit. After 5 minutes, things cool down, lights come back on, only to repeat every few minutes.
Kent
