Lennox ResolvePlus Rooftop Unit Error Codes
Lennox ResolvePlus packaged rooftop units use a flashing LED diagnostic system on the integrated control board. The control stores up to 5 fault codes in memory. For units with Lennox communicating thermostats (iComfort), fault codes display as numeric codes directly.
ResolvePlus Fault Code Table
| Code | Fault Description | Common Cause | Action |
|---|---|---|---|
| 111 | Pressure switch fault | Blocked inducer, failed switch | Measure flue pressure |
| 114 | Limit switch open | Dirty filter, blocked return | Replace filter, check airflow |
| 125 | Ignition failure | Low gas, weak igniter | Check gas pressure and igniter |
| 204 | High-pressure switch open | Dirty condenser coil | Wash coil, check fan operation |
| 223 | Low-pressure switch open | Low refrigerant charge | Check charge, inspect TXV |
| 225 | Freeze fault | Low airflow or refrigerant | Check filter and evaporator coil |
| 231 | Discharge temperature high | Refrigerant issue, condenser fan | Inspect condenser fan motors |
| 327 | Communication fault | Wiring issue to communicating thermostat | Check communication wiring |
| 332 | Blower motor fault | Failed ECM motor or VFD | Check motor for proper operation |
| 411 | Flame sensor fault | Dirty or failed flame sensor | Clean sensor, measure ┬╡A |
| 412 | Inducer motor fault | Failed inducer motor | Check inducer amp draw |
| 432 | Gas valve fault | Failed gas valve | Check 24 VAC at valve |
| 540 | Loss of communication | Communication board or wiring | Inspect communication connections |
Most Common ResolvePlus Faults
Code 114 — Limit Switch Open
Check the air filter first. ResolvePlus units are sensitive to static pressure — a dirty filter or blocked return can trip the limit at low ambient temperatures. Verify blower motor speed matches installed ESP.
Code 125 — Ignition Failure
Check inducer operation before gas pressure. If the inducer doesn’t prove, the gas valve won’t open. Verify inducer pressure switch closes (typically -0.30 to -0.45 in. w.c.).
Code 204 — High-Pressure Switch
On R-410A units, high-side pressure above 590 psi trips the HP switch. Wash the condenser coil, verify condenser fan rotation and amp draw.
Parts Commonly Needed
| Part | Notes |
|---|---|
| Integrated control board | Amazon | Must match unit model |
| Flame sensor | Amazon | Measure ┬╡A before replacing |
| Inducer motor | Amazon | Check capacitor first |
| Limit switch | Amazon | Match temperature rating |
| ECM blower motor | Amazon | Check motor module and control board |
Pro tip: Lennox ResolvePlus fault history is accessible via the field diagnostic tool or iComfort interface. Always retrieve fault history before clearing codes to identify intermittent problems.
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