Lennox Error Codes | HVAC IQ Pro

201 critical

Limit Switch Open

Probable Causes

Dirty filter
Blocked return
Bad blower
Limit switch failure

Diagnostic Steps

Replace filter
Check ductwork
Test blower
Check limit

227 critical

No Flame Sensed

Probable Causes

Dirty flame sensor
Bad igniter
Gas supply issue
Control board

Diagnostic Steps

Clean flame sensor
Check igniter
Verify gas
Test board

270 critical

High Pressure Switch Open

Probable Causes

Dirty condenser
Overcharge
Restriction
Fan failure

Diagnostic Steps

Clean condenser
Check fan
Check charge

271 critical

Low Pressure Switch Open

Probable Causes

Low charge
Frozen coil
Restriction
TXV failure

Diagnostic Steps

Check charge
Check filter
Check TXV

292 critical

Compressor Lockout

Probable Causes

Thermal overload
Bad capacitor
Locked rotor

Diagnostic Steps

Let cool down
Test capacitor
Check amps

E201 high

Control Self-Diagnostics Failure

Probable Causes

Control board failure
Power surge damage

Diagnostic Steps

Power cycle furnace
Check for proper voltage
Replace control board if persists

E225 critical

Roll-Out Switch Open

Probable Causes

Heat exchanger crack
Blocked heat exchanger
Gas overpressure

Diagnostic Steps

STOP - potential CO hazard
Inspect heat exchanger for cracks
Check gas pressure
Manual reset rollout switch

E227 medium

External Low Voltage Short

Probable Causes

Thermostat wire short
Bad thermostat
Wire damage

Diagnostic Steps

Disconnect thermostat wires
Check for shorts at furnace terminals
Inspect wire routing

E228 high

Blocked Vent/Pressure Switch

Probable Causes

Blocked flue/intake
Failed pressure switch
Inducer motor failure
Condensate drain blocked

Diagnostic Steps

Inspect flue pipe and intake for blockage
Check condensate drain
Test pressure switch
Measure inducer amps

E250 critical

Ignition Failure / No Flame Detected

Probable Causes

No gas supply
Dirty flame sensor
Bad igniter
Gas valve failure

Diagnostic Steps

Verify gas is on
Clean flame sensor
Check igniter glow
Test gas valve voltage

E269 critical

Limit Switch Circuit Lockout

Probable Causes

Repeated high temp trips
Chronic airflow issue
Oversized unit

Diagnostic Steps

Must manually reset
Check airflow thoroughly
Inspect ductwork
Verify unit sizing

E270 high

High Limit Switch Open

Probable Causes

Dirty filter
Blocked return air
Bad blower motor
Oversized gas orifice

Diagnostic Steps

Check and replace filter
Verify return air is open
Test blower motor
Check gas pressure

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