M42 Battery Light

[TPS]

Recently my dashboard Battery Light, has developed an intermittent fault, when starting from cold it sometimes won't light up, the battery & alternator have been tested & are producing 14 volts. Fitted a new BMW drivebelt, as the other one screeched & was stretched, any ideas what this might be?

[Brianmoooore]

Obvious answer is that the bulb has blown!

[chippy1947]

maybe a diode in the alternator going faulty cant see a blown bulb intermittently coming back on

[Brianmoooore]

It's entirely possible, and very common, for a blown low voltage bulb with a short thick filament "intermittently coming back on" when subjected to vibration.
The broken ends of the filament shake around, and if they happen to touch, the resultant magnetic field created when the current flows will hold the two ends together until another shock separates the ends, or the current is cut off.

[TPS]

Thanks for the advice everyone, what bulb do I need for this?

[Brianmoooore]

Little capless 1.2W bulb, the same as fitted for all the other warning lights and illumination for ashtrays, etc. 286 is the type number.

[TPS]

Thanks Brian