York HVAC Error Codes: Complete Diagnostic List
10 diagnostic codes documented · Official site ↗
🟡 Warning — Schedule Service
Improper Thermostat Wiring
The A4 error code on your York furnace indicates a problem with the thermostat wiring. The furnace's control board isn't seeing the correct signals from your thermostat, which tells it when to turn on and off. This can happen if the wires are loose, shorted, or connected to the wrong terminals. Because the furnace relies on these signals to operate safely and efficiently, it will shut down to prevent potential problems. Specifically, the A4 error often points to issues with the 24VAC control circuit. This circuit is responsible for communicating between the thermostat and the furnace's control board. If the board detects an unexpected voltage or a break in the circuit, it will trigger the A4 error and prevent the furnace from running. This is a safety feature to protect the furnace from damage and prevent it from running erratically.
Pressure Switch Stuck Closed
The "R2" error code on your York furnace indicates that the pressure switch is stuck in the closed position. This switch is designed to prove that the inducer motor is creating enough suction to safely vent exhaust gases outside your home. When the furnace starts, the inducer motor turns on, creating a vacuum that pulls the pressure switch closed. The control board expects this switch to be open before the inducer starts and close once the inducer is running. If the switch is already closed before the inducer starts, the control board assumes something is wrong and locks out the furnace to prevent potentially dangerous operation. This could mean the switch is faulty, there's a blockage in the venting, or an issue with the inducer motor itself. Because the furnace won't run, you'll have no heat until this is resolved.
Pressure Switch Stuck Open
The R3 error code on your York furnace indicates that the pressure switch is stuck in the open position. This switch is a safety device that verifies the furnace's exhaust fan (inducer motor) is working correctly before allowing the burners to ignite. When the inducer motor starts, it creates a slight vacuum that closes the pressure switch, signaling to the control board that it's safe to start the ignition sequence. If the switch remains open, the furnace control board will prevent ignition and display the R3 error. This is a safety feature to prevent the furnace from operating improperly, which could lead to a dangerous buildup of exhaust gases inside your home.
High Limit Switch Open
The R4 error code on your York furnace indicates that the high limit switch has opened. This switch is a critical safety device designed to shut down the furnace if it gets too hot. Think of it like a circuit breaker for heat. When the furnace temperature exceeds a safe threshold, the high limit switch trips, cutting off the gas supply and blower motor. This prevents potential damage to the furnace components and, more importantly, protects your home from a fire hazard. The R4 code means the furnace control board detected that the switch is open (tripped). It's important to address the underlying cause of the overheating, not just reset the system.
🔴 Critical — Shut Down Immediately
Low Flame Current
The 'AF' error code on your York furnace indicates a low flame current. This means the furnace's control board isn't detecting a strong enough electrical signal from the flame sensor. The flame sensor is a safety device that proves the burners have lit. If the sensor doesn't detect a proper flame, the furnace should shut off the gas valve to prevent a dangerous accumulation of unburned gas inside the unit. This error can occur intermittently or cause a complete lockout of the furnace, preventing it from heating your home. Because it relates to gas combustion, it's important to address this issue promptly and safely.
Flame Without Call
The 'R1' error code on your York furnace, labeled 'Flame Without Call,' means the furnace control board is sensing a flame present in the burner assembly even when there's no active call for heat. In simpler terms, the furnace thinks it's burning gas when it shouldn't be. This is a dangerous situation because it could lead to uncontrolled gas flow, overheating, or carbon monoxide buildup. It's important to address this issue immediately to prevent potential hazards and further damage to your furnace. This error typically forces the furnace to lock out, preventing it from operating until the problem is resolved.
Rollout Switch Open
The R5 error code on your York furnace indicates that the rollout switch has tripped. This switch is a critical safety device designed to shut down the furnace if it detects flames where they shouldn't be – specifically, outside the normal burner area. This is a serious issue because it means there's a risk of fire or carbon monoxide poisoning. The rollout switch is a small, often red, button located near the burners. When it senses excessive heat from a 'rollout' flame, it opens the circuit, cutting off gas flow to the burners. Ignoring this error can lead to dangerous conditions, so it's important to address it immediately.
Gas Valve Failure
The R6 error code on your York furnace indicates a 'Gas Valve Failure'. This means the furnace control board isn't detecting the gas valve opening or closing properly, or that the valve isn't responding to the board's commands. The gas valve is responsible for safely controlling the flow of natural gas to the burners for combustion. If the valve malfunctions, it can either prevent the furnace from heating or, more seriously, cause a dangerous buildup of gas. Because natural gas is both flammable and can cause carbon monoxide poisoning, this is a serious issue that needs immediate attention.
Ignition Lockout
The R7 error code on your York furnace indicates an 'Ignition Lockout'. This means the furnace attempted to ignite the burners multiple times but failed. After several failed attempts, the control board locks out the ignition sequence as a safety measure to prevent a dangerous buildup of gas. This lockout can be triggered by various issues within the ignition system or problems with the gas supply itself. Continuing to try and reset the furnace without addressing the underlying problem is risky and could lead to a hazardous situation. It's important to address this issue promptly to restore heat and ensure safe operation.
Reversed Polarity
The R9 error code on your York furnace indicates a reversed polarity issue. This means the hot and neutral wires are connected incorrectly somewhere in the electrical circuit powering your furnace. This is a serious safety hazard because it can energize the metal parts of the furnace, creating a risk of electric shock. It can also damage the furnace's control board and other components. Your York furnace relies on proper electrical polarity to operate safely and reliably. When the polarity is reversed, the furnace's safety mechanisms may not function correctly, potentially leading to a fire or explosion. Do not attempt to troubleshoot this issue yourself. Contact a qualified professional immediately.