YellowS4DHC wrote:Tony,
Given that the bulb is good and the alternator is new, I'd be inclined to check the ground connection of the ignition warning light before I anything else.
Use a volt/ohm meter to check the ground connection resistance. Or, simply attach one end of an 18 or 20 gauge wire to a known good ground and the other end to the warning light ground attach point on the back of the tach. If the light glows like it should when the ignition is switched on, problem identified.
If not, then you need to do some serious head scratching.
regards
Rick
'72 Europa TC
'69 Elan S4 DHC
'67 S800 Coupe
'57 T1 Speedster
Rick,
That isn't how ignition warning lights work on a Lucas / Elan set up.
The ignition warning light isn't earthed, it has two wires going to an insulated plastic bulb holder. One wire goes to the switched side of the ignition key, the other to the alternator.
When the ignition key is switched on, current flows through the bulb to the alternator and the bulb lights. After starting, as the alternator voltage builds up, current flow is reduced and the bulb goes out.
To the O/P, Bob's recommended checks (post above) are the way to go about testing the system.
Good luck.