Burners will not light or stay lit - Carrier 58SB0A/58SB1A

What is going on

Ignition-proving problems (codes 34 and 14) worked through with the component test.

Likely causes

• Gas valve or manual shutoff off
• Igniter or harness open
• No 24 V to gas valve or valve stuck
• Low inlet pressure or poor carryover
• Dirty, grounded or weak flame sensor
• Control fault

Check in this order

1. Check the gas valve switch and the manual shutoff, the green/yellow ground to sheet metal, and that the flame sensor is not touching ground.
2. Remove the R lead and run the component test; the igniter should glow orange/white by the end of its 15 s warm-up.
3. No glow unplug the igniter harness and check for 115 V from pin 1 to neutral during the test; voltage present means replace the igniter or harness, none means replace the control.
4. Put R back and call for heat; the gas valve should get 24 V. No 24 V: check wiring, then the control.
5. 24 V but no gas flow: replace the valve. Gas flows but no ignition: check inlet pressure, firing rate, burner carryover gap (about .045 in.).
6. Burners light then drop measure flame current; typical is 4.0-6.0 microamps. Under 0.5 microamps: clean the sensor with fine steel wool or replace it.
7. If current is normal and burners still drop out, replace the control.

More furnace guides

• Furnace not responding to thermostat - Carrier 58SB0A/58SB1A