Lennox error codes
39 documented codes with ranked causes, repair costs, and step-by-step guidance.
Lennox heat pump code chart (5) Lennox furnace code chart (34)
Lennox Heat Pump — Stuck in defrost mode Lennox Heat Pump Stuck in Defrost Mode: Causes & Fixes Lennox heat pump stuck in defrost? Learn the causes (defrost board, sensor, reversing valve, relay), safe checks, and repair costs from $0 to $1,500+. Lennox Heat Pump — Frozen and not defrosting Lennox Heat Pump Frozen and Not Defrosting: Fixes & Cost Lennox heat pump iced over and not defrosting? Learn the causes (water drips, defrost sensor, board, reversing valve), safe checks, and repair costs. Lennox Heat Pump — Ice on outdoor unit Lennox Heat Pump Ice on Outdoor Unit: Causes & Fixes Ice on your Lennox heat pump's outdoor unit? Learn normal frost vs. problem icing, the likely causes, safe checks, and repair costs from $0 to $3,000+. Lennox Heat Pump — Not cooling Lennox Heat Pump Not Cooling: Causes, Fixes & Costs Lennox heat pump not cooling? Ranked causes like reversing valve, capacitor, low refrigerant and dirty coils, safe checks, and honest repair costs. Lennox Heat Pump — Not heating Lennox Heat Pump Not Heating: Causes, Fixes & Costs Lennox heat pump not heating? Causes like thermostat setup, defrost, low refrigerant or stuck reversing valve, safe checks, and repair costs. Lennox Furnace — Pressure switch stuck open Lennox Furnace Pressure Switch Stuck Open: Fixes & Cost Lennox furnace pressure switch stuck open: causes from blocked vents to a failing inducer, safe DIY checks, pro fixes, and real US repair costs. Lennox Furnace — Runs constantly but not enough heat Lennox Furnace Runs Constantly But Not Enough Heat Lennox furnace runs nonstop but can't keep up: dirty filter, undersized ducts, flame issues & more. DIY checks, pro fixes, and costs from $0 to $3,500+. Lennox Furnace — Won't ignite Lennox Furnace Won't Ignite: Causes, Fixes & Costs Lennox furnace won't ignite? Causes include a failed igniter, dirty flame sensor, closed gas valve and pressure switch faults — fixes and costs inside. Lennox Furnace — Blower not running Lennox Furnace Blower Not Running: Causes & Fixes Lennox furnace blower not running? Causes include a bad capacitor, blower motor, control board or door switch, plus fixes and US repair costs. Lennox Furnace — Clicking but not starting Lennox Furnace Clicking But Not Starting: Causes & Fixes Lennox furnace clicking but not starting? Causes include a stuck pressure switch, weak igniter, dirty flame sensor or open safety. Fixes and $0–$1,200 costs. Lennox Furnace — Blower won't shut off Lennox Furnace Blower Won't Shut Off: Causes & Fixes Lennox furnace blower runs constantly? Causes include thermostat fan settings, an open limit switch, or a stuck relay. DIY checks plus $0–$1,200 repair costs. Lennox Furnace — Flame sensor problems Lennox Furnace Flame Sensor Problems: Fixes & Costs Lennox furnace flame sensor problems cause dropouts and lockouts from a dirty or failed sensor. Cleaning runs $80-$180; replacement $150-$300. Lennox Furnace — Ignition lockout Lennox Furnace Ignition Lockout: Causes, Fixes & Costs Lennox furnace ignition lockout causes—igniter, flame sensor, gas supply, pressure switch—plus safe checks, tech diagnosis, and repair costs from $0 to $1,200. Lennox Furnace — Keeps shutting off Lennox Furnace Keeps Shutting Off: Causes, Fixes & Costs Lennox furnace keeps shutting off? Causes include dirty filters, flame sensor, limit and pressure switch faults — fixes and US repair costs. Lennox Furnace — Leaking water Lennox Furnace Leaking Water: Causes, Fixes & Costs Lennox furnace leaking water? Causes include clogged condensate drains, cracked traps and flue issues, plus fixes and honest US repair costs. Lennox Furnace — Loud bang on startup Lennox Furnace Loud Bang on Startup: Causes & Fixes A loud bang when your Lennox furnace ignites usually means delayed ignition or duct oil-canning. Safety steps first, then causes, checks, fixes and costs. Lennox Furnace — Short cycling Lennox Furnace Short Cycling: Causes, Fixes & Costs Lennox furnace short cycling? Common causes include dirty filters, overheating limits, flame sensor issues and oversizing—with fixes and US cost ranges. Lennox Furnace — Won't turn on Lennox Furnace Won't Turn On: Causes, Fixes & Costs Lennox furnace won't turn on? Common causes from thermostat and power to blown fuses and failed boards, with DIY checks and honest US repair costs. Lennox Furnace — Code E209 Lennox Furnace Code E209: High Fire Pressure Switch Fix Lennox Code E209 means the high-fire pressure switch failed to close. Causes, safe checks, tech diagnosis and repair costs from $0 DIY to $1,200 or more. Lennox Furnace — Code E240 Lennox Furnace Code E240: Low Flame Current Fix & Cost Lennox Code E240 means low flame current in run mode from a dirty flame sensor or weak flame. Causes, fixes and honest US costs inside. Lennox Furnace — Code E250 Lennox Furnace Code E250: Limit Switch Open Fix & Cost Lennox Code E250 means the primary limit circuit is open from restricted airflow or overheating. Causes, safe checks, fixes and US repair costs. Lennox Furnace — Code E270 Lennox Furnace Code E270: Ignition Retry Lockout Fix Lennox furnace Code E270 means max ignition retries exceeded. Learn causes, safe checks, technician diagnosis and repair costs from $0 to $1,200. Lennox Furnace — Code E125 Lennox Furnace Code E125: Control Self-Check Failure Fix Lennox furnace Code E125 means the control board failed its internal self-check. Learn causes, safe checks and board replacement costs. Lennox Furnace — Code E206 Lennox Furnace Code E206: Gas Valve Relay Fix & Cost Lennox Code E206 means a second-stage gas valve relay failure. Learn causes, safe checks, technician fixes and honest US repair costs.