Intermittent alternator and dashlight failing '87 W460. How do trace fault?

Hi All,

Had long-term intermittent issues with alternator not charging (and been left stranded on a couple of occasions). Anyway, mistakes aside (like replacing alternator having not appreciated the clues the dashlight was giving), determined fault somewhere in the circuit supplying the 12V exciter lead that also illuminates the battery light on dashboard (did this by running a 12V jumper lead to alternator and hey presto all works fine). The bulb is fine (removed in picture), but how can I test contunuity when can't see any connectors to power bulb? 

Suspect I'm missing something obvious, but any clues or thoughts to help resolve would be appreciated?

There is a multi-pin connector supplying the cluster, it might help to now what number (wire colour?) corresponds to the battery light? I did have a quick look at wiring diagrams, but I'm no electrician, not even sure looked at correct part!

Would be great to put battery charger back on shelf! Any help please?

Cheers,

Stewart