Lennox Error Code 8: Control Board Error
Warning: Your Lennox HVAC system has a control board issue that requires professional repair.
LED Blink Pattern
LED blinks 8 times.
How to Fix Lennox Code 8
- Step 1: Turn off your HVAC system at the thermostat and the main power switch.
- Step 2: Check if the control board is securely fastened and all wires are properly connected.
- Step 3: Call a professional Lennox technician to diagnose and repair the issue.
How to Reset Lennox Code 8
- 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 8 Mean?
Error code 8 on your Lennox HVAC system indicates a problem with the control board. The control board is the brain of your system, managing all its operations. This error could be due to a faulty board itself or an issue with its wiring or components. It's important to address this issue promptly to prevent further damage or system failure.
Common Causes
- Faulty control board
- Loose or damaged wiring connected to the control board
- Defective components on the control board
- Power surges or voltage fluctuations
Diagnostic Steps
| If... | Check | Expected |
|---|---|---|
| Control board is not securely fastened | Tighten the screws and recheck the error | Error should resolve |
| Wiring is loose or damaged | Inspect all wires connected to the control board | Tight and undamaged wires |
| Power supply to control board is fluctuating | Measure the voltage at the control board | Stable 24V AC |
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 | 40-123456-00 | — | Find Part |
Related Codes on Same Models
Other codes that affect the same Lennox model families as 8.
| 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 |
| 9 | Line Voltage Polarity Incorrect | Warning |
| E250 | Lennox Code E250 - Indoor Blower Communication Error | Warning |