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I got so involved with explaining why the AMP light comes ON, that I didn't why it may NOT come on. First, and before you start suspecting major components, it MAY be as simple as a burned out lamp...pop the lamp holding socket out of back of instrument cluster to check and replace.

To correct an incorrect point made: The lamp must have a good connection, yes, but it is not "earthed in its socket". Socket is an isolated type...were two wires leave the socket. AMP light is used in a slightly unusual way...under normal conditions, both sides of the lamp have voltage applied (Therefore: no voltage across, lamp stays OFF). One side is supplied by Ignition Power, the other side senses Generator output at terminal D+ of Regulator. Amp light gets voltage across it to light it when there is no Generator output with Ignition ON (like before starting, or after gen failure), or when power from Fuse 1 goes away (blown fuse, or poor connection for instance).

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