It must be the fuse. Or there is a short somewhere.
4x6 in the front dash
Check the fuses, check the bulbs but first, be sure the dash light dimmer control is not turned off.
if it is the top light in the center of the dash it is the chock on light
The alternator is failing.
under the dash
There'll be an indicator light on the dash which comes on when the high beam circuit is energized.
Analog dash IA a 1991 chevy s-10 blazer
Behind the passenger side of the dash.
Under dash, drivers side.
Under the left side of dash.
Be sure the dash illumination dimmer switch is not turned off.
could be several reasons, dash light dimmer switch is turned off or bad, bulbs are blown out or fuse is blown out.