An error code is a way for an HVAC system (like a mini-split or central unit) to communicate that something isn’t working properly. Instead of just shutting down with no explanation, the system will flash a specific code.
Each error code points to a specific issue, like:
-
Electrical problems
-
Sensor malfunctions
-
Communication failures between components
-
Refrigerant pressure issues
-
Motor faults
-
Temperature problems
Signature Series Packaged Units:
| MPH Models: | MPC Models: |
|
MPH241M414A |
MPC241M414A |
| MPH301M414A | MPC301M414A |
| MPH361M414A | MPC361M414A |
| MPH421M414A | MPC421M414A |
| MPH481M414A | MPC481M414A |
| -- | MPC601M414A |
Diagnostic Codes:
| Green LED (DS2) | Red LED (DS1) | Condition |
| Off | Off | No Power to Control |
| Simultaneous Slow Flash💥 | Simultaneous Slow Flash💥 | Normal Operation/Power to Control |
| Alternating Slow Flash💥 | Alternating Slow Flash💥 | 5-Min Anti-Short-Cycle Delay |
| On | Slow Flash💥 | Low Pressure Switch Ignored (Low Ambient) |
| Off | Slow Flash💥 | Low Pressure Switch Fault |
| Off | On | Low Pressure Switch Lockout |
| Slow Flash💥 | Off | High Pressure Switch Fault |
| On | Off | High Pressure Switch Lockout |
・・・──────────────────────────────・・・
Signature Series Packaged Gas Electric:
| Models: |
| MPG30S054M414A |
| MPG36S090M414A |
| MPG42S090M414A |
| MPG48S108M414A |
| MPG60S108M414A |
Diagnostic Codes:
| LED Status | Flashing Rate | Description |
| Slow Flash💥 | One Flash Per Second | Normal Operation: No Call for Heat |
| Fast Flash💥 | Two Flashes Per Second | Normal Operation: Call for Heat |
| 2 Flash💥 | Two Flashes per Second with 1-Second Pause | System Lockout: Failed to Detect or Sustain a Flame |
| 3 Flash💥 | Three Flashes per 1.5 second with 1 Second Pause | Pressure Switch Senses Incorrect Pressure or Gas Valve Coil is Open |
| 4 Flash💥 | Four Flashes per 2 Seconds with 1- Second Pause | High Limit or Rollout Switch is Open |
| 5 Flash💥 | Five Flashes per 2.5 Seconds with 1- Second Pause | Flame Sensed and Gas Valve Not Energized |
| Steady Flash💥 | -- | Internal Failure: Micro-Controller Failure; Self Check |
・・・──────────────────────────────・・・
Signature Split Heat Pump Condensers:
| Models: |
| MHP15018A |
| MHP15024A |
| MHP15030A |
| MHP15036A |
| MHP15042A |
| MHP15048A |
| MHP15060A |
Diagnostic Codes:
| Green LED (DS2) | Red LED (DS1) | Description |
| Off | Off | No Power to Control |
| Simultaneous Slow Flash💥 | Simultaneous Slow Flash💥 | Normal Operation/ Power to Control |
| Alternating Slow Flash💥 | Alternating Slow Flash💥 | Anti-Short Cycle Lockout |
| Off | Slow Flash💥 | Low Pressure Switch Fault |
| Off | On | Low Pressure Switch Lockout |
| Slow Flash💥 | Off | High Pressure Switch Fault |
| On | Off | High Pressure Switch Lockout |
・・・──────────────────────────────・・・
Furnaces:
| Downflow 96% AFUE | Multi Position 96% AFUE | Multi Position 80% AFUE |
| MGD96SE045B3XA | MGM96SE045B3XA | MGM80SE045A3A |
| MGD96SE070B4XA | MGM96SE070B3XA | MGM80SE070B3A |
| MGD96SE090C4XA | MGM96SE090C4XA | MGM80SE090B4A |
| MGD96SE110C5XA | MGM96SE110C5XA | MGM80SE090C5A |
| -- | MGM96SE135D5XA | MGM80SE110C5A |
| -- | -- | MGM80SE135D5A |
Diagnostic Codes for Control Board 103217-03:
Heartbeat= Slow Flash- 1 Second on and 1 Second off Repetitively
Error Codes= Rapid Flashes roughly every half a second
| Red LED | Description |
| Off | No Power to Control or Control Hardware Fault Detected |
| Heartbeat | Normal Operation- Idle, Continuous Fan, Cool |
| Continuous Rapid Flash💥 | Call for heat/ Burner Operation |
| 1 Flash💥 | Reverse Line Voltage Polarity |
| 2 Flashes💥 | Improper Earth Ground |
| 3 Flashes💥 | Burner Failed to Light, or Lost Flame During Heat Demand |
| 4 Flashes💥 | Low Flame Signal- Check Flame Sensor |
| 5 Flashes💥 | Watchguard- Burner Failed to Light, Exceeded Maximum Number of Retries or Recycles |
| 6 Flashes💥 | Not Used |
| 7 Flashes💥 | Primary or Secondary Limit Open or Watchguard Mode- Limit Switch Open Longer than 3 Minutes |
| 8 Flashes💥 | Rollout Switch Open |
| 9 Flashes💥 | Pressure Switch Failed to Close or Open During Heat Demand |
| 10 Flashes💥 | Watchguard- Pressure Switch Opened 5 Times During One Heat Demand |
| 11 Flashes💥 | Pressure Switch Stuck Closed Prior to Activation of Combustion Air Inducer |
| 12 Flashes💥 | Flame Sensed Without Gas Valve Energized |
| 13 Flashes💥 | Low line Voltage |
Diagnostic Codes for Control Board 107163-01:
Slow Heartbeat= Slow Flash- 1 Second on and 1 Second off Repetitively
Fast Heartbeat= Fast Flash- 1/2 Second on and 1/2 Second off
Error Codes= Rapid Flashes roughly every half a second
| Red LED | Description |
| Off | No Power to Control or Control Hardware Fault Detected |
| On | Board Fault Detected |
| Fast Heartbeat💥 | Call for Heat/ Burner Operation |
| Slow Heartbeat💥 | Normal Operation- Idle, Continuous Fan, or Cool |
| 1 Flash💥 | Reverse Line Voltage Polarity or Phasing of 120V Power |
| 2 Flashes💥 | Improper Earth Ground |
| 3 Flashes💥 | Burner Failed to Light or Lost Flame During Heat Demand |
| 4 Flashes💥 | Low Flame Signal- Check Flame Sensor |
| 5 Flashes💥 | Watchguard- Burner Failed to Light, Exceeded Maximum Number of Retries/ Recycles, 1 Hour Lockout |
| 6 Flashes💥 | Not Used |
| 7 Flashes💥 | Primary or Secondary Limit Switch Open or Watchguard Mode- Limit Switch Open Longer than 3 Minutes |
| 8 Flashes💥 | Rollout Switch Open |
| 9 Flashes💥 | Pressure Switch Failed to Close or Open During Heat Demand |
| 10 Flashes💥 | Watchguard- Pressure Switch Opened 5 Times During One Heat Demand |
| 11 Flashes💥 | Pressure Switch Stuck Closed Prior to Activation of Combustion Air Inducer |
| 12 Flashes💥 | Flame Sensed Without Gas Valve Energized |
| 13 Flashes💥 | Low Line Voltage |
・・・────────────────・・・
| Downflow 95% AFUE | Multi Position 95% AFUE | Downflow 80% AFUE |
| MGD95SE045B3XA | MGM95SE045B3XA | MGD80SE045A3A |
| MGD95SE070B4XA | MGM95SE070B3XA | MGD80SE070B3A |
| MGD95SE090C4XA | MGM95SE090C4XA | MGD80SE090B4A |
| MGD95SE110C5XA | MGM95SE110C5XA | MGD80SE110C5A |
| -- | MGM95SE135D5XA | -- |
Diagnostic Codes for Control Board -02:
Heartbeat= Slow Flash- 1 Second on and 1 Second off Repetitively
| Red Led | Description |
| Off | No Power to Control or Control Hardware Fault Detected |
| Heartbeat💥 | Normal Operation- Idle, Continuous Fan, Cool |
| 1 Flash💥 | Reverse Line Voltage Polarity |
| 2 Flashes💥 | Improper Earth Ground |
| 3 Flashes💥 | Burner Failed to Light, or Lost Flame During Heat Demand |
| 4 Flashes💥 | Low Flame Signal- Check Flame Sensor |
| 5 Flashes💥 | Watchguard- Burner Failed to Light, Exceeded Maximum Number of Retries or Recycles |
| 6 Flashes💥 | Not Used |
| 7 Flashes💥 | Primary or Secondary Limit Open or Watchguard Mode- Limit Switch Open Longer than 3 Minutes |
| 8 Flashes💥 | Rollout Switch Open |
| 9 Flashes💥 | Pressure Switch Failed to Close or Open During Heat Demand |
| 10 Flashes💥 | Watchguard- Pressure Switch Opened 5 Times During One Heat Demand |
| 11 Flashes💥 | Pressure Switch Stuck Closed Prior to Activation of Combustion Air Inducer |
| 12 Flashes💥 | Flame Sensed Without Gas Valve Energized |
| 13 Flashes💥 | Low Line Voltage |
Diagnostic Codes for Control Board -03:
Heartbeat= Slow Flash- 1 Second on and 1 Second off Repetitively
Error Codes= Rapid Flashes roughly every half a second
| Red LED | Description |
| Off | No Power to Control or Control Hardware Fault Detected |
| Heartbeat💥 | Normal Operation- Idle, Continuous Fan, Cool |
| Continuous Rapid Flash💥 | Call for heat/ Burner Operation |
| 1 Flash💥 | Reverse Line Voltage Polarity |
| 2 Flashes💥 | Improper Earth Ground |
| 3 Flashes💥 | Burner Failed to Light, or Lost Flame During Heat Demand |
| 4 Flashes💥 | Low Flame Signal- Check Flame Sensor |
| 5 Flashes💥 | Watchguard- Burner Failed to Light, Exceeded Maximum Number of Retries or Recycles |
| 6 Flashes💥 | Not Used |
| 7 Flashes💥 | Primary or Secondary Limit Open or Watchguard Mode- Limit Switch Open Longer than 3 Minutes |
| 8 Flashes💥 | Rollout Switch Open |
| 9 Flashes💥 | Pressure Switch Failed to Close or Open During Heat Demand |
| 10 Flashes💥 | Watchguard- Pressure Switch Opened 5 Times During One Heat Demand |
| 11 Flashes💥 | Pressure Switch Stuck Closed Prior to Activation of Combustion Air Inducer |
| 12 Flashes💥 | Flame Sensed Without Gas Valve Energized |
| 13 Flashes💥 | Low line Voltage |
✅ Why Error Codes Matter:
They help technicians, installers, and even homeowners quickly understand where to start troubleshooting without guessing.
✅ Important Tip:
While error codes point you in the right direction, they don’t always tell you the exact part that’s failed — just the general area or type of problem. Further testing is often needed!
Comments
0 comments
Please sign in to leave a comment.