07-10-2020, 07:00 PM
(This post was last modified: 07-10-2020, 07:01 PM by Ian McGowan.)
Blowing bulbs is invariably a consequence of excess voltage being applied to them. The lead acid battery, with its exceedingly low internal resistance acts as a "sink" to stabilise the output from the dynamo. A usual cause of bulbs blowing is a situation where the battery becomes disconnected from the circuit thus allowing the voltage to rise to well above normal. Operating a battery isolator switch with the engine running can be a cause.