Weird fault battery warning lamp fault

Been dangling with a fault these last few weeks. Started out as the battery warning lamp flickering.
By coincidence or not both headlamps blew a night after
When going about 120kmh the dash would light all lamps and the hippo would take a nose dive.

Till now: alternator ok, ECU ok, Wiring ok.
Suspect: instrument cluster

Any ideas?

How's the main earth at the battery, body and engine points?

was loose but now solid as a rock

and is the warning light staying off now? to see if the alternator is on the way out ,at night put on your lights full on with the engine running and any other things like radio and extra lamps then put you foot on the brakes ,if the alternator light is showing a dim glow that it is on its way out hope this helps

The only things that will cause the charge light to stay on are a duff alternator or just possibly bad connections from the engine to chassis or battery. Lights coming on and other things tend to suggest alternator regulator or diode pack failing.

Tried both but to no avail. Bought a new cluster as that is our next bet after the ecu, will try it out this week. Thanks guys. This problem is really breaking my brains