rebuilding 10 d pack

I'm replacing the batteries in an old video light pack (with nicads, thank you ikelite staff for the info). There is a problem with the pack however, the pack lights both the main and modelling light on the modelling light switch position, (main light position is fine)the other battery pack I have does not do this, so I know it's the pack, not the light. The wiring looks good, but it looks like there is a diode heat shrinked in the modelling light wiring. Before ripping it all apart, is this a plain power diode? (eg not a zener diode), and would this cause the described problem if defective?
Thanks

The two most likely suspects are either the bulkhead is wired incorrectly or the diode is installed with the wrong polarity. If the diode is in backwards it may have failed as a short circuit. The diode is a 1N5819 Schottky diode.

Regards,
Jean / Ikelite
IKELITE Underwater Systems