I have a 10 year old Amana (GUD070X30B) , White-Rodgers 50A50-288 Control.
The thermostat calls for heat, the gas turns on and runs for approx 15 minutes then the gas
shuts off but the thermostat is still calling for heat. The inducer motor is still running and the
diagnostic light is 3 Blinks saying the Pressure switch is stuck open (caused by the inducer motor still running). If I set the thermostat below the set temperature and wait 5 min. before setting the thermostat above current temp the furnace will again go through the same cycle.

hvac1000

Could be a defective pressure switch. Take a pressure test tool and test the switch to see if it functions. Sometimes a small piece of hose will work. Suck or blow into the hose to see if you can make it work.