[V8] Consoll lights go dead!

[Peter A. Green]

Somebody must have experienced this one!
At night I am driving along, headlights on, and suddenly the lights in the consol go dead.  It's quite a strange feeling without the friendly glow of the lights!  If I turn off the lights the usual daylights come-on - radio, heater, dash shifter selector etc.  In the morning, the lights behave normally, until the headlights are used continuously.  Anyone BTHT?
Suggestions greatly appreciated - except 'sell the beast!"
Pete
V8Q '90 Pearl