104
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. You will see the protection function actually cause the unit to slow down outside if discharge temperature is too high. Both compressor and van will ramp down.
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. Skip to 4.
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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: Look for signs of a leak. If you see low suction pressure(Less that 110 psi) in cooling or low pressure in heating(Less than 400 PSI) , you likely have a leak. Remember to have you in test mode(Fan High and temperature setpoint all the way up or down) before looking at pressures. Unit needs to run in test mode for at least 10-12 minutes. Also, in heating mode, if the indoor fan does not ramp up, that is again another sign of low head pressure/ low refrigerant.
