Carrier Gas Furnace: 58SX

Re: Burners Fire then Shut Off

The furnace goes through a normal ignition sequence, but several seconds after ignition the burners shut off.

CHECKOUT:

1. Check Low Voltage

• Check for 24VAC power between "R" and "C" on the terminal block.
• Monitor power through the ignition sequence.
  • Power Drops Out When Burners Shut-Off = Limit Switch Opening
  • Power Stays On but Burners Shut-Off ⇒ Continue
• Check for 24VAC power between "W" and "C" on the terminal block.
• Monitor power through the ignition sequence.
  • Power Drops Out When Burners Shut-Off = Thermostat Short-Cycling
  • Power Stays On but Burners Shut-Off → Step 2. Check Pressure Switch

2. Check Pressure Switch

• With the inducer motor running, check for 24VAC at the pressure switch between COM (ORG) and "C".
  • Power Drops When Burners Shut-Off = Bad Control Board
  • Power Stays On and Burners Shut-Off ⇒ Continue
• With the inducer motor running, check for 24VAC at the pressure switch between N/O (BRN) and "C".
  • Power Drops When Burners Shut-Off = Pressure Switch Problem
  • Power Stays On and Burners Shut-Off → Step 3. Check 3-Wire Pilot

3. Check 3-Wire Pilot

• At the 3-Wire Pilot plug, check for 24VAC between COM (YEL) and "C".
  • Power Drops When Burners Shut-Off = Bad Inducer (IDR) Board
  • Power Stays On and Burners Shut-Off ⇒ Continue
• At the 3-Wire Pilot plug, check for 24VAC between N/O (WHT) and "C".
  • Power Drops When Burners Shut-Off = Bad 3-Wire Pilot or Bad Heat Exchanger
  • Power Stays On and Burners Shut-Off = Bad Gas Valve