Lennox Error Code 6: Pressure Switch System Lockout
Warning: Your Lennox HVAC system has a pressure switch system lockout, which means it's not running to prevent damage. Call a professional soon.
LED Blink Pattern
LED blinks 6 times.
How to Fix Lennox Code 6
- Step 1: Check and replace your air filter if it's dirty
- Step 2: If the system still won't run, call a professional HVAC technician
How to Reset Lennox Code 6
- 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.
Resetting clears the code from the display but does not fix the underlying fault. If the code returns after reset, proceed to the diagnostic steps above.
What Does Lennox Error Code 6 Mean?
The Lennox 6 error code indicates that the system's pressure switch has detected an abnormal pressure condition, causing the system to shut down. This could be due to a clogged filter, a refrigerant leak, or a faulty pressure switch. It's important to address this issue promptly to prevent further damage to your HVAC system.
Common Causes
- A clogged air filter restricting airflow
- A refrigerant leak causing low pressure
- A faulty pressure switch sending incorrect signals
Diagnostic Steps
| If... | Check | Expected |
|---|---|---|
| System won't run | Air filter condition | Clean and unrestricted |
| Low refrigerant pressure | Refrigerant leak | No leak detected |
Applicable Lennox Models
- Lennox Healthy Climate(dual_fuel)
- Dave Lennox Signature Collection(gas)
- EL296(electric)
- EL296V(electric)
- ELP(electric)
- Elite Series(electric)
- G61(gas)
- Health Saver Series(electric)
- ML195(dual_fuel)
- ML199(gas)
- NCB(electric)
- NPE(electric)
- Pace Series(electric)
- SLO(gas)
- SLP(electric)
- SLP98(gas)
- SLP98V(gas)
- Slimline Series(electric)
Replacement Parts
| Part | OEM Number | Est. Cost | Where to Buy |
|---|---|---|---|
| Pressure Switch | 42-0227-00 | — | Find Part |
Related Codes on Same Models
Other codes that affect the same Lennox model families as 6.
| Code | Description | Severity |
|---|---|---|
| 1 | Ignition Failure | Warning |
| 2 | Pressure Switch Stuck Closed | Warning |
| 3 | Pressure Switch Stuck Open | Warning |
| 4 | High Limit Switch Open | Warning |
| 5 | Flame Rollout Switch Open | 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 |