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Home > Error Codes > Ruud
Every documented Ruud furnace error code with causes, fixes, and the parts you may need. Also covers: Ruud.
Steady ON
Replace Control Board
Internal control board failure. The board cannot operate the furnace.
DIY check: Power cycle first. If steady ON persists, the control board needs replacement.
Common part needed: Shop Control Board →
Steady OFF
Check Power
No power reaching the control board.
DIY check: Check breaker, furnace switch, door switch, board fuse, and transformer.
Common part needed: Shop Transformer →
1 Flash
Ignition Lockout
The furnace failed to ignite after maximum retries. System locked out.
DIY check: Power cycle to reset. Check gas supply, igniter condition, and flame sensor cleanliness.
Common part needed: Shop Igniter →
2 Flashes
Pressure Switch Stuck Closed
Pressure switch is closed before inducer operation. Switch may be stuck or hose may have water in it.
DIY check: Tap the pressure switch gently. Check for water in the hose. Replace if it sticks repeatedly.
Common part needed: Shop Pressure Switch →
3 Flashes
Pressure Switch Open
Pressure switch did not close after inducer started. Most common Ruud error code.
DIY check: Check condensate drain, vent blockage, pressure hose, inducer motor. Clear the trap first.
Common part needed: Shop Pressure Switch →
4 Flashes
Flame Rollout Switch Open
The flame rollout safety switch tripped. Flame was detected outside the combustion chamber.
DIY check: Do NOT simply reset and run. Have a technician inspect the heat exchanger and burners. Could indicate a cracked heat exchanger.
5 Flashes
Low Flame Signal
Flame is present but the sensor reading is weak (below ~1.5 microamps).
DIY check: Clean the flame sensor with emery cloth. Check the sensor wire connection. Replace the sensor if cleaning does not improve the signal.
Common part needed: Shop Flame Sensor →
6 Flashes
115V Power Reversed
Line and neutral are reversed at the furnace.
DIY check: Check and correct the wiring polarity at the furnace junction box.
7 Flashes
High Limit Switch Open
Overheating detected. Limit switch tripped due to restricted airflow or failed blower.
DIY check: Check air filter, supply registers, blower wheel, and blower motor.
Common part needed: Shop Fan Motor →
8 Flashes
Low Flame at 2nd Stage
On two-stage furnaces, the flame signal drops below acceptable when switching to high fire.
DIY check: Clean flame sensor. Check gas pressure at both stages. May need gas valve adjustment (technician).
Common part needed: Shop Flame Sensor →
9 Flashes
Gas Valve Relay Error
The gas valve relay on the control board has failed or the valve circuit is open.
DIY check: Check gas valve wiring. Test the gas valve coil. If the relay on the board has failed, the board needs replacement.
Common part needed: Shop Gas Valve →
10 Flashes
Blower Motor Fault
The blower motor did not reach the expected speed or failed to start.
DIY check: Check blower motor, run capacitor, and wiring. On ECM motors, check the motor module.
Common part needed: Shop Fan Motor →
11 Flashes
Flame Without Call for Heat
Flame detected without a thermostat demand. The gas valve may be leaking.
DIY check: Turn off furnace and gas immediately. Call a technician.
Common part needed: Shop Gas Valve →
12 Flashes
Flame Lost During Run
The flame was established but then lost during the heating cycle. Different from Code 5 (weak signal) - here the signal dropped to zero.
DIY check: Check gas supply pressure (may be intermittent). Clean flame sensor. Check for drafts or wind affecting the burner flame.
Common part needed: Shop Flame Sensor →
13 Flashes
Communication Error
Communication fault between the control board and an accessory or communicating thermostat.
DIY check: Check thermostat wiring. Verify the thermostat is compatible with the furnace. Check for damaged wires.
14 Flashes
Power Interrupted to Board
The control detected a momentary power loss that did not fully reset the board. May cause erratic behavior.
DIY check: Check for loose wiring connections at the furnace. Ensure the circuit breaker and switch connections are tight.
If the same code keeps coming back after you have addressed the obvious cause (dirty filter, flame sensor, etc.), or if you smell gas, see burn marks, or the furnace will not come out of lockout after a power cycle, call a licensed HVAC technician. Electrical and gas work carries real safety risk.