WaterFurnace · No longer sold new in the UK. 8 codes across 1 product family, each taken from the manufacturer’s manuals. WaterFurnace technical support ↗
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Type the code on your display or a word from its meaning. Each code opens its own page with what it means, whether it is safe and what you can check.
8 codes
| Code | Meaning | Stops? | Homeowner check? |
|---|---|---|---|
| B0 | Brown-Out (B0): Control voltage falls below 18VAC for 10-15 continuous seconds; all operation disabled | Yes | Yes |
| dC | Freeze Detection Probe Closed (dC): Freeze detection probe closed or no resistance; compressor and pump disabled | Yes | Yes |
| dO | Freeze Detection Probe Open (dO): Freeze detection probe open or infinite resistance; compressor and pump disabled | Yes | Yes |
| FP | Freeze Detection (FP): Refrigerant loop temperature below the FP value (service menu) for 30 continuous seconds; compressor and loop pumps disabled; 2-minute bypass at start-up | Yes | Yes |
| HC | Water Temperature Probe Closed (HC): Control senses the water probe is closed or no resistance; compressor and pump disabled | Yes | Yes |
| HP | High Pressure (HP): Normally closed high-pressure switch opened momentarily; compressor disabled immediately; displayed only after two retries and lockout; pump continues to run during retries | Yes | Yes |
| LP | Low Pressure (LP): Normally closed low-pressure switch open for 30 continuous seconds (bypassed 2 min after start-up); displayed after two retries and lockout | Yes | Yes |
| PO | Water Temperature Probe Open (PO): Control senses the water probe is open or infinite resistance; compressor and pump disabled | Yes | Yes |