Yeah, the headlight switch is usually the culprit, but if you have tail lights then that's not the problem.
The Panel Lamp Control Module is behind the instrument panel, left side. I've never seen one cause I've never had one go bad, but my diagram indicates the module has 2 wire bundles going from it with 2 connectors, one over to the dimmer switch, the other to connect to the instrument panel lighting.
Disconnect that lighting connector, should be yellow and white w/4 wires, near?? the module behind the instrument panel. On the connector side NOT going to the module, jump the red with black stripe wire (12 volts with lights on) to the 2 red with green stripe wires. Black wire is ground.
Should work. I never use the dimmer either.
Probably not this week, but when If I get a chance I'll tear into my parts car and pull that module so I'm smarter about Capri wiring...Chris