My ac doesnt work,its blowing HOT air all the time even when turned off. on 1998 Chevrolet S10

a/c was working fine . turned it on one day and it was blowing hot air . Tried to make sure thermostat was turned to cool but still blowing hot . Also a/c is turned off and hot air is still blowing.

2 answers
stuck heater control valve
poss heater control valve stuck open start there