Lennox Error Code 3: Pressure Switch Stuck Open
Warning: Your Lennox HVAC system has detected a pressure issue that requires professional attention.
How to Fix Lennox Code 3
- Step 1: Check your air filter. If it's clogged, replace it with a new one.
- Step 2: If your system has a reset button, try pressing it to see if that clears the error.
- Step 3: If the error persists, do not attempt to fix it yourself. Call a professional HVAC technician.
How to Reset Lennox Code 3
- Turn off the furnace power switch, usually located on or near the unit.
- Turn off the circuit breaker for the furnace. Wait 30 seconds.
- Restore power at the breaker and flip the furnace switch back on.
- Set the thermostat to call for heat. If the error code returns after 2-3 ignition attempts, the fault requires repair.
What does 3 mean?
Lennox error code 3 indicates that the pressure switch is stuck open. This switch is a safety component that monitors the system's pressure and prevents it from operating if there's a refrigerant leak. When it's stuck open, it's as if the system thinks there's a leak, even if there isn't. This can cause your system to lock out and not operate properly. This issue is typically caused by a faulty pressure switch or a problem with the system's pressure, such as a clogged filter or a refrigerant leak.
Affected Models
- SLP98V
- SLP98
- EL296V
- EL296
- SLP
- SLP
- ELP
- ELP
- NCB
- NPE
- Elite Series
- Elite Series
- Dave Lennox Signature Collection
- Dave Lennox Signature Collection
- ML195
- SLO
- EL296
- SLP98V
- EL296V
- G61
- ELP
- NCB
- NPE
- NPE
- ML195
- ML199
- Elite Series
- Dave Lennox Signature Collection
- Lennox Healthy Climate
- Elite Series
- Elite Series
- Slimline Series
- Slimline Series
- Health Saver Series
- Pace Series
Replacement Parts
| Part | OEM Number | Est. Cost |
|---|---|---|
| Pressure Switch | 40-000011-00 | — |
Related Codes on Same Models
| Code | Description | Severity |
|---|---|---|
| 1 | Ignition Failure | Warning |
| 2 | Pressure Switch Stuck Closed | Warning |
| 4 | High Limit Switch Open | Warning |
| 5 | Flame Rollout Switch Open | Warning |
| 6 | Pressure Switch System Lockout | Warning |
| 7 | Ignition Lockout | Warning |
| 8 | Control Board Error | Warning |
| 9 | Line Voltage Polarity Incorrect | Warning |
| E250 | Lennox Code E250 - Indoor Blower Communication Error | Warning |