equipo5 wrote:
The electrics work ok with the headlight hanging out but once in, it shorts out. Maybe created by the compression of the wiring as you say.
For clarity, I believe you mean the "circuit opens up". If the headlight was working when you tried re-installing it, that means that current stopped flowing through the bulb filament. This can happen two ways: First, if the current is interrupted by a bad connection somewhere or secondly if the current finds another easier path to ground than through the filament.
The first, an interruption in the current flow through the filament is referred to as an open circuit. In the second case the current finds and easier way around the filament on it's way to the negative post of the battery. This would be a short circuit.
If the circuit opens up then nothing will happen and the bulb will simply go out. If, on the other hand, the current finds an easier path around the filament that would commonly show up as sparks or heated wires which burn up their insulation.
Since you said nothing about smoke or fire I suspect that the current path has opened up somewhere between the battery positive post and the battery negative post. The likely place for the fault is in the headlight shell since that's where you were working at the time. You could have a broken wire, a corroded or dirty electrical connection, a loose screw or nut, or maddeningly an intermittent condition such as a broken filament inside the bulb sometimes touching together and sometimes not.
But the chances are that in moving the headlight around you are jiggling a faulty connection, either on the positive or "high" side of the bulb or on the "low" side.
It might be a good idea to take apart each electrical connection and clean it, putting some dielectric grease on the connection. (Home Depot, perhaps an auto parts store, Radio Shack, etc.)
I apologize if I am "talking down" to you in the above. Simply, I don't know you and your electrical expertise.
Ken
It's bigger than the $20 alternative they also list for the 75/5. 
