HVAC Error Code Guide
Your HVAC system is flashing an error code — what does it mean? Our error code guide explains common codes from major brands and tells you when to call a professional.
Error Codes by Brand
Carrier
Carrier Error Code 33 — What It Means & How to Fix It
Error code 33 on a Carrier furnace indicates that the limit circuit is open. This is a safety mechanism that shuts down the furnace when it detects overheating. The furnace's limit switch trips to prevent the heat exchanger from cracking due to excessive temperatures — a serious safety concern that can lead to carbon monoxide leaks.
View DetailsCarrier
Carrier Error Code 13 — Limit Circuit Lockout
Error code 13 on a Carrier furnace means the system has entered limit circuit lockout. This occurs when the limit switch has tripped repeatedly (typically 3 times in a row), causing the furnace to lock out for safety. This is a more serious version of error code 33 — the furnace won't attempt to restart automatically.
View DetailsTrane
Trane Error Code E1 — Communication Failure
Error code E1 on a Trane HVAC system indicates a communication failure between the indoor and outdoor units or between the thermostat and the system. Trane's communicating systems (ComfortLink II and XV series) rely on a communication wire connecting all components. When this communication breaks down, the system may stop heating or cooling entirely.
View DetailsLennox
Lennox Error Code E201 — Pressure Switch Fault
Error code E201 on a Lennox furnace indicates a pressure switch fault. The pressure switch is a safety device that verifies the inducer motor (draft fan) is running and creating proper venting before allowing the gas valve to open. When the pressure switch can't confirm proper draft, the furnace won't ignite.
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