I have a Bryant 80 furnace , had the ignitor replaced in November. Since then the furnace will power up, ignitor and burners will go and then when the blower turns on the burners go out, the blower will go for about 90 seconds and then shut down. It will do this repeatedly sometimes as many as 30 times. The LED code flashes 12. I have had the company that replaced the ignitor come out they have cleaned the flame sensor and replaced the pressure switch. The furnace will run fine for weeks then the problem will start again. Any ideas what the problem might be?

I don't know all the codes in my head, did you look for answer on the blower door? What's it say?

Code say "Blower on after power up. Blower runs for 90 sec if unit is powered up during a call for heat . (R-W Closed)

Make sure your not losing power going to the furnace. Check bottom door on furnace to make sure its secured and closing the door switch. Check to see if your main power wires are getting good connection near the top in a small junction box they wire nut them together. It sounds like a power interruption problem. Did you add an extra outlet or appliance to the furnace circuit that may have it overloaded?

Packaged unit burners fire run for 3 minutes blower motor does not run until flame goes out then the unit cycles with the igniter, burners on for 3 minutes then burners go out then the indoor blower motor runs for maybe a 1 minute then the units cycles indoor blower motor will not run with the burners on. What is the problem thermostat?