| Diagram | Fig. 21 — ELECTRICAL EQUIPMENT (Plate 14) · ref 74 |
| Listed in parts books | 1969–1970 |
BSA Zener diode
A zener diode from the charging system electrics, used to bleed off excess current and protect the battery.
This is a zener diode, part of the charging system on the electrics side of the bike. It shows up in the electrical equipment figures in the parts books for 1969-1970 machines, doing the job of shedding excess current from the alternator so the battery doesn't get cooked once the engine's running fast enough to overcharge.
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On these older British bikes without a proper regulator setup, the zener diode is the component that keeps voltage in check. It's usually bolted to a heat sink somewhere it can get some airflow, since it dumps the extra current as heat.
Our catalog record ties this one to 1969-1970 appearances across a few electrical equipment plates. If you're chasing a charging fault or a battery that keeps boiling over, this is one of the usual suspects to check, but confirm the exact fitment for your bike before ordering.
We've never carried this one. Tell us what you're after and we'll go looking — you'll get a price and photos before you commit to anything.
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