| Diagram | Fig. 35 — ELECTRICAL COMPONENTS · ref 15 |
| Listed in parts books | 1969–1970, 1973, 1975–1977 |
Zener diode (49345)
A zener diode (99-0590) used in the charging system to bleed off excess current and protect the battery on older Triumph electrics.
This is a zener diode, part number 99-0590, listed among the electrical components on Triumphs across a run of catalog years from 1969 into 1977. In this era of British bike wiring, the zener diode does the job a modern voltage regulator would do — it bleeds off excess charging current so the system doesn't overcharge the battery and cook the electrics.
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On these machines the zener diode usually mounts to a finned heat sink somewhere out in the airflow, since it dumps the excess current as heat. It shows up across several electrical figures in the parts books alongside the ignition coils, horn, and rectifier, which tells you it's grouped with the rest of the charging and ignition hardware rather than living in the headlamp shell itself.
Beyond that, the catalog record doesn't spell out a specific model or year for this exact part - it just shows this diode appearing in electrical component listings over a several-year span. If you're replacing one, check what rectifier and alternator setup you're running before you order, since the zener has to be matched to the rest of the charging system.
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