The tachometer circuit consists of a sensor at the crankshaft front pulley, the signal amplifier (round black canister) on the left inner fender wall, and the tachometer guage. The amplifier is usually the part that is the problem, losing electrical contact. Search this forum for more information. There has been much discussion on repairs. Also, check to make sure no fuse has burned out or gone bad.

Have heard that later cars, 1984 and 1985 use a different circuit for the tachometer, integrating it into the EGR system. But your 1982 should have the canister and sensor.

Not sure if you did anything to damage the tachometer by removing the air cleaner. Probably just a coincidence.