Lennox Error Code 9: Line Voltage Polarity Incorrect
Warning: Your Lennox HVAC system has detected an incorrect line voltage polarity, which could lead to system damage if not addressed.
LED Blink Pattern
LED blinks 9 times.
How to Fix Lennox Code 9
- Step 1: Turn off the power to your HVAC system at the circuit breaker.
- Step 2: Check the wiring connections at the control board and ensure they are properly connected and not reversed.
- Step 3: If you're unsure about any electrical work, contact a professional Lennox technician.
How to Reset Lennox Code 9
- 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 9 Mean?
The Lennox 9 error code indicates that the line voltage polarity in your HVAC system is incorrect. This means that the positive and negative wires are reversed, which can cause system malfunctions and potential damage to the components. It's important to have this issue resolved promptly to prevent further problems.
Common Causes
- Incorrect wiring during installation or repair
- Wiring damage due to age, pests, or environmental factors
- Faulty control board or other electrical components
Diagnostic Steps
| If... | Check | Expected |
|---|---|---|
| HVAC system is not functioning | Measure the voltage at the control board using a multimeter | 120V AC, with correct polarity |
| Voltage is present but system is not functioning | Inspect the wiring connections at the control board for any signs of damage or reversed polarity | Tight, undamaged connections with correct polarity |
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 |
|---|---|---|---|
| Control Board | 43A101745 | — | Find Part |
| Wiring Harness | — | — | — |
Related Codes on Same Models
Other codes that affect the same Lennox model families as 9.
| 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 |
| 6 | Pressure Switch System Lockout | Warning |
| 7 | Ignition Lockout | Warning |
| 8 | Control Board Error | Warning |
| E250 | Lennox Code E250 - Indoor Blower Communication Error | Warning |