Series 3 ignition light on.

[COW1980]

Hi All,

Hopefully somebody can provide some help.

I currently playing with 1972 series 3, and currently having trouble with the ignition light on dimly, although charging at 13.8 to 14.2 volts.

I have been through the forum, and been through the checks and found that I only have around 9 volts from the F+ terminal and presume this voltage difference across the lamp is causing it to been on. Light goes off if I unplug the regulator, but will stay on very dimly if I unplug the F+ terminal from the alternator but leave the multi plug connected on the Voltage regulator, (which is new) with the engine not running, but ignition on. I can also get the light to go off if I flash battery voltage to the positive terminal of the voltage regulator which obviously feeds the lamp with the engine running.

Engine harness is new, and all earths have been checked, volt drop carried and as well as resistance checks and can’t find any faults, have also confirmed using jump leads as earths on the engine and chassis. Wiring connections triple checked. Also has the the filament type lamp fitted.

I’m currently leaning towards and internal fault on the Butec Alternator?

Thanks,

Chris

[MarekH]

.... although charging at 13.8 to 14.2 volts.....

... I only have around 9 volts from the F+ terminal and presume this voltage difference across the lamp is causing it to been on.

I’m currently leaning towards and internal fault on the Butec Alternator?

The F+ terminal is fed by the white triple diode block mounted on the on the front exterior of the unit and one diode has gone open circuit. That'd explain why you have 9v on F+

Stick a multimeter both ways across each of the three inputs to the white block and its output and verify all three diodes are still sound. I'd have thought only two of the three are working.

kind regards
Marek