The original red ignition warning light fitted between the Tacho and Speedometer on later rubber bumper MGBs have been unavailable for some time. MGOC Spares & Accessories stock aftermarket replacement lamps supplied with an attractive chrome ring,
Also available in Green - Indicator (AAU4824Z), and Blue - Main
Beam (AAU3858Z). The original retaining clip is available separately (BHA5125).
Uses GLB287 Bayonet bulb
Ignition Warning Light Trouble Shooting
At low RPM the alternator requires a voltage supply from the battery via the ignition light circuit to energise the stator within the alternator in order that the alternator can produce a charge. Because a conventional filamenet bulb is effectively a resistor it can pass voltage from the battery to the alternator to energise the stator, a Light Emitting Diode (LED) however passes current one way only i.e it cannot pass voltage from the battery to the alternator, so the circuit cannot energise the stator and create a charge. If an LED is fitted within the warning lamp circuit the ignition warning light will stay on and the alternator will not charge below 2500rpm. When the rpm is raised above 2500rpm the alternator self-energises dispensing with need for supply via the ignition warning light circuit and the LED will go out. The issue has only recently come to 'light' with owners alterring their dash bulbs to LED.