Hello, I have a Bryant 373LAV that started giving me a code 34. I removed and cleaned the flame sensor, problem still existed, the since the system it over 10 years old I replaced the Flame sensor. The system fired up for about 30 minutes the shut off with a code 34. I removed the green wire to the frame and cleaned both surfaces to ensure a good connection. Restarted the system with the same results.
Blower fan comes on
The smaller fan come on (I think it's a flue fan)
Igniter comes on
Gas ignites
Flames are a nice blue
After about 2 seconds the system shut down
Every now and then it will run longer but not over 30 minutes.
I have to work on the system at night after work so it take me a bit to try any suggestions...