Furnace Service Manuals

Gas Furnaces (All Brands)

• No Heat – 3 LED Flashes (Pressure Switch): Check vent blockage, condensate drain, restricted intake; test pressure switch.
• No Heat – Flame Rollout / Limit Open: Dirty flame sensor (clean with steel wool); clogged air filter; blower failure.
• Ignitor Glows but No Flame: Check gas valve voltage (24V); cracked hot surface ignitor; dirty flame sensor.
• Short Cycling: Overheated – replace dirty filter; check return air size; limit switch tripping.

Goodman / Amana / Daikin

• 1 Blink: Ignition failure – clean flame sensor
• 2 Blinks: Pressure switch stuck closed
• 4 Blinks: High limit / rollout open
• Continuous Blink: Reversed polarity or poor ground

Carrier / Bryant / Payne

• LED Code 33 / 13: Limit circuit fault – dirty filter or blower speed too low
• LED Code 24: Secondary voltage fuse open
• LED Code 14 / 34: Ignition lockout – clean flame sensor

Trane / American Standard

• 2 Flashes: System lockout (retries/recycles exceeded)
• 4 Flashes: Open high limit device
• 6 Flashes: Flame sensed when no flame should be present

Oil Furnaces (Beckett, Riello, Carlin Burners)

• Lockout (Red Button): Press reset once only; check oil tank, filter, nozzle, bleed air from line.
• No Ignition: Clean electrodes (3/16" gap); replace nozzle annually.

Note: Always turn off power before servicing. For persistent issues, contact a licensed HVAC technician.