Run capacitor
Common no-start and weak-compressor failure point. Match the microfarad and voltage rating.
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 microA |
| 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 | Must match unit model |
| Flame sensor | Measure microA before replacing |
| Inducer motor | Check capacitor first |
| Limit switch | Match temperature rating |
| ECM blower motor | Check motor module and control board |
Technician Tips
For ResolvePlus rooftop-unit faults, match the alert to the packaged-unit sequence: economizer, blower, condenser fan, pressure switch, ignition module, gas heat, or rooftop control board.
Need Replacement Parts?
Before ordering, match the HVAC part to the model number, electrical rating, and failure symptom. Check current prices on Amazon - prices and availability change frequently.
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.