I have a 350MAV036060F Bryant Plus 90 furnace whose blower had stopped working and control board LED was flashing 31.
I could cycle the emergency switch to reset but after a couple mins it would shutdown and flash 31 again. Having checked the meaning of code, I performed the following:
1. Checked the vents and intake PVC lines to ensure no blockage.
2. Checked the lines on the pressure switch.
3. Checked the condensate trap.
4. Checked the filter condition.
Not having solved the problem, I saw somewhere online I can test if the blower motor is good by jumping L1 and the blue 'heat' line. When I did that I heard a soft humming sound and the yellow LED went off. Fearing that I had messed up the control board (HK42FZ014), I bought one online and replaced it properly only to find that the LED is still off. I checked the 3A fuse on both old and new boards and it appears good. I used my multimeter and I am getting 120V coming thru the door switch when I tape it shut. I do not get any voltage going to the capacitor and thus no 24V coming out of it. HELP PLEASE!!