Lennox Gas Furnace: G24M3
Re: Diagnostic Codes / Lockout Codes
There are 2 possible control boards on this furnace - a dual light board (Red & Green) and a single LED board.
| ORIGINAL BOARD | |
| Single-Light Furnace Control Board Fault Conditions | |
|
LED |
Description |
| Steady On | Control Board Failure (Replace Control) |
| Slow Flash | Normal Operation - No Call For Heat |
| Fast Flash | Normal Operation - Call For Heat |
| 2 Flashes | Lockout - Failed to Sense or Sustain Flame |
| 3 Flashes | Pressure Switch Open |
| 4 Flashes | Open Limit |
| 5 Flashes | Flame Sensed with Gas Valve Off |
| REPLACEMENT CONTROL BOARD | ||
| Dual-Light Furnace Control Board Fault Conditions | ||
|
DS1 (Red) |
DS2 (Green) |
Description |
| Simultaneous Slow Flash | Power On - No Call For Heat | |
| Simultaneous Fast Flash | Normal Operation - Call For Heat | |
| Slow Flash | On | Primary or secondary limit switch open. Limit must close within 3 minutes or unit goes into 1−hour Watchguard. |
| Off | Slow Flash | Pressure Switch Fault: Open with inducer on or Closed with inducer off. |
| Alternating Slow Flash | Watchguard −− Burners failed to ignite, limit open longer than 3 minutes, or flame sense lost 5 times in one heating cycle. |
|
| Slow Flash | Off | Flame sensed without gas valve energized. |
| On | Slow Flash | Rollout switch open. |
| On | On |
Control Board Failure or Control Mis-Wired. Check 24V and 115V Wiring Connections. |
| Off | On | |
| On | Off | |
| Fast Flash | Slow Flash | Main power polarity reversed. Switch line and neutral. Improper main ground. |
| Slow Flash | Fast Flash | Low flame signal. Check flame sensor. |
| Alternating Fast Flash | The following conditions are sensed during the ignitor warm−up period only: 1) Improper main ground; 2) Broken ignitor; OR: Open ignitor circuit; 3) Line voltage below 75 volts. |
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