I've got issues...

if the system only gets a few amps because of a bad ground the kight might be just enough to draw the current away from the gasmeter .
it might whell be that if you disconect the front lightbulbs from the wiring the gauge come back on same as the dashlights

i had the smae problem but it was due to bad conection at the plug and plastic board at the guages either dirty or plg cam loose and feeding of other circut

my vote is on a burned circuit board due to a bad ground-either a chassis ground or in the headlight switch.