The dimmer switch typically dies somewhere along the lines.
Even so, by comparison to today's led illuminated dash boards, even functioning correctly, the Pantera's is pretty dim.
The basic premise of using a green background doesn't help matters at all.
Go to Pantera-electronics.com and look at the led replacements for the old 12v bulbs.
You can inquire with Jon as to how to test and what to do about the dimmer.