UPDATE:FIXED! Inspected left and right side wiring harness and noticed the left harness had some play in it. Removed the yellow clip and pushed the blue harness forward a little more and then locked it in place. Plugged everything back in and now all is well.[/QUOTE]
Just for anyone visiting this page like I did many years later, it's also worth checking the electrical connections where the indicator bulb holder connects to the headlight cluster, as this can become loose and give an intermittent indicator bulb failure, and is easy to confuse with the symptoms listed above.
This is the testing procedure I followed to identify this issue in my car - posting to help others..
- Remove the offending headlamp unit and confirm the continuity of the offending blub.
- Test for current at the wing-connection to the headlight referenced in jonny3303's post above by getting a test lamp to illuminate (the indicators are the second pair of female connectors from the top on the car side).
- Remove the indicator bulb holder from its recess and the electrical plug that connects it to the headlamp (see pic).
- Bridge the two male connections on the headlamp-side of the connection and test for continuity at the poles on the indicator end (ie. testing the headlamp unit itself).
- Then test for continuity between the bulb holder and the electrical plug that connects it to the headlamp.
- Supply power direct to the male headlamp connections (crocodile clips connected via a battery) and squeeze the plastic shroud (black plastic connector) that holds the electrical plug to the underlying poles. If the bulb illuminates the shroud has become loose causing an intermittent failure.
- Remove the shroud (black plastic connector) entirely, solder new connections that provide a strong interference fit to the poles, insulate them, and reassemble everything.
