HOME and how to join Forum Open Area General Scott topics Late Shipley ignition warning light. Re: Re: Late Shipley ignition warning light.

Stan Thomas

I’m afraid that is not correct.

In basic terms, the ignition warning light is powerd by a positive polarity feed when the ignition is turned, and is “earthed” to negative polarity via the field coils of the stationary dynamo. When the dynamo begins to rotate, a positive polarity is produced in the field coils, thus depriving the the warning light of a negative polarity return, so it goes out.

As the dynamo speed rises, it would continue to produce a rising voltage unless limited by the regulator – until internal resistance levels this off at around 30 volts. (which incidentally is why you can instantly convert to a 12 volt system, given a change in regulators etc.)

Dependent upon condition and adjustment etc. of the (mechanical) regulator, this is why the warning light sometimes appears to increase its brightness until the regulator cuts in to limit the dynamo voltage output. To avoid any momentary “over-voltage”, a protective resistance is sometimes incorporated into the warning light circuit.