10-10-2020, 10:42 PM
(10-10-2020, 04:34 PM)JonE Wrote: Could a fault in the dynamo itself also cause the light to stay extinguished? I have quite similar symptoms now! I've checked 'earth' to ignition light (to PLC switch) but am getting same high discharge and no light when ignition turned on. Light was operating fine initially and discharge nothing to speak of when ignition turrned on.
have you checked the bulb side of the circuit by disconnecting the wire from the dynamo's D terminal and touching it to a good chassis connection? The bulb should light if the ignition switch end of the circuit is good. The ignition light has battery voltage behind it via the ignition switch it and the dynamo D connection in front of it. When you turn on the ignition the bulb illuminates to earth via the non charging dynamo, when you start the car the dynamo output rises and the bulb dims and then is extinguished as the voltage rises.
The big discharge the OP is seeing is almost certainly caused by a sticking cutout where the battery is sinking power through the dynamo's armature when the dynamo's output drops.