99 1.8 Intermittent headlight failure - The Grey Man

The nearside headlight on my MX-5 is intermittently working. The police pulled me over for it yesterday and yet later in the day it was fine. When it was not working both the small side light bulbs in the headlight were ok but the main bulb was not on. When I drove home from work I checked....it was off at the start of the journey yet working when I got home 5 miles later. There is no problem with the offside headlight.

Could this conceivably be a problem with the bulb that replacing it might fix or is it likely a loose electrical connection which is a worry as these things I expect are difficult to diagnose.

99 1.8 Intermittent headlight failure - mjm
I would be looking at a dirty connection onto the bulb or a bad earth. Unplugging the connector to the bulb and cleaning the contacts would be my first job. I would remove the bulb from the lamp, plug it into the connector, turn the light on and waggle the bulb about to see if it went off. (Keep hands off the glass part of the bulb, it'll get v hot).

I'm assuming that yours is the fixed headlight mark 2a, not pop up headlights. If it's pop ups then the security of the loom would be my next port of call.