My dash light went out on my 1990 buick century.

Hello, the fuse for the lighter is in the IP fuse block marked LTR it is a 20 amp yellow fuse. the ip fuse block is on the passenger side of dash panel

Do you have power coming out of the headlight switch for those two circuits ?

You may have a blown fuse.

if you have the owners manual it should give proper amp and location of fuses otherwise check both sides of each fuse with a test light for power when you find the one with power only on one side remove and replace that fuse the lighter fuse should have power with key off some fuses need key on to light up at all and some will need items such as headlights turned on to light

I would guess it is metric,as are most all bolts,except some large size chassis bolts,and have been since about 1983. You got rust issues also.

Probably located in end of dash,opendrivers door panel on end of dash should pop open.

CHECK YOUR TAIL LAMP/ILLUMINATION FUSE, YOUR TAIL LAMPS & DASH LIGHTS ARE ON THE SAME CIRCUIT

I suspect the light switch.

Your turn signal flasher should be located under the dash on just to the right hand side of the steering column. It we most likely be a round little can shaped object

the stop/brake light switch is located at the top of the arm that the brake pedal is mounted on, you may have to pull the trim panel off under the dash to see it

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