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Fujitsu Error 10.1 (Discharge Temperature)
10 - 1 Flash code
A1 Code at thermostat
Description: This error occurs when the discharge pipe thermistor senses a temperature exceeding the safety limit (typically around 230°F/110°C). It is a protective stop to prevent compressor failure.
Common Causes
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Low Refrigerant Charge: The most frequent culprit. Low mass flow means the compressor can't stay cool, causing "superheated" discharge gas.
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Dirty/Clogged Indoor Blower Wheel: If the wheel is caked with dust (especially in Heat Mode), it can't move enough air across the coil to remove heat, driving up the discharge temp.
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Dirty Outdoor Coil: If the condenser is blocked, it can't reject heat properly, leading to high head pressure and high discharge temps.
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Faulty Discharge Thermistor: The sensor itself may be out of calibration (ohm-out is required). Or it may be loose.
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Expansion Valve (EEV) Failure: If the EEV is stuck closed or restricted, it starves the compressor of cool suction gas. This can also cause a 10.3 error as well.
Troubleshooting Flow
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Step 1: The "10-Minute Reset": Kill the breaker for at least 10 minutes. If the error returns immediately upon compressor startup, check the sensor. If it takes a few minutes, look for a mechanical/charge issue.
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Step 2: Check the Blower Wheel: Physically inspect the indoor unit’s blower wheel. A "fuzz-covered" wheel is a leading cause of this error in the winter.
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Step 3: Ohm the Thermistor: Disconnect the discharge thermistor from the PCB and check resistance. Use Fujitsu App for reference measurement.
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Step 4: Check Pressures/Superheat: Look for signs of a leak. If you see high superheat and low suction pressure, you likely have a leak at the flare or the indoor coil.
