Danfoss VLT FC 101 Fault Codes List

Access the complete reference guide for Danfoss VLT HVAC Basic FC 101 fault codes. Learn to diagnose Fire Mode alarms, distinguish Trip Locks, and use MCT 10.

Danfoss FC 101 Fault Codes Reference Table

Fault Code	Cause & Solution
WARNING 2 Live zero error	Cause: This warning or alarm only appears if parameter 6-01 Live Zero Timeout Function is configured. The signal on 1 of the analog inputs is less than 50% of the minimum value programmed for that input. This condition can be caused by broken wiring or a faulty device sending the signal. Troubleshooting: - Check connections on all the analog input terminals. Control card terminals 53 and 54 for signals, terminal 55 common. - Check that the frequency converter programming matches the analog signal type.
ALARM 2 Live zero error	Cause: This warning or alarm only appears if parameter 6-01 Live Zero Timeout Function is configured. The signal on 1 of the analog inputs is less than 50% of the minimum value programmed for that input. This condition can be caused by broken wiring or a faulty device sending the signal. Troubleshooting: - Check connections on all the analog input terminals. Control card terminals 53 and 54 for signals, terminal 55 common. - Check that the frequency converter programming matches the analog signal type.
WARNING 3 No motor	Cause: No motor is connected to the output of the frequency converter. Solution: - Check the cable connection between the frequency converter and the motor.
ALARM 3 No motor	Cause: No motor is connected to the output of the frequency converter. Solution: - Check the cable connection between the frequency converter and the motor.
WARNING 4 Mains phase loss	Cause: A phase is missing on the supply side, or the mains voltage imbalance is too high. This message also appears for a fault in the input rectifier on the frequency converter. Options are programmed at parameter 14-12 Function at Mains Imbalance. Troubleshooting: - Check the supply voltage and supply currents to the frequency converter.
ALARM 4 Mains phase loss	Cause: A phase is missing on the supply side, or the mains voltage imbalance is too high. This message also appears for a fault in the input rectifier on the frequency converter. Options are programmed at parameter 14-12 Function at Mains Imbalance. Troubleshooting: - Check the supply voltage and supply currents to the frequency converter.
WARNING 7 DC overvoltage	Cause: If the DC-link voltage exceeds the limit, the frequency converter trips after a time. Troubleshooting: - Extend the ramp time. - Activate functions in parameter 2-10 Brake Function. - Activate overvoltage control in parameter 2-17 Over-voltage Control.
ALARM 7 DC overvoltage	Cause: If the DC-link voltage exceeds the limit, the frequency converter trips after a time. Troubleshooting: - Extend the ramp time. - Activate functions in parameter 2-10 Brake Function. - Activate overvoltage control in parameter 2-17 Over-voltage Control.
WARNING 8 DC under voltage	Cause: If the DC-link voltage (DC) drops below the under voltage limit, the frequency converter trips after a fixed time delay. The time delay varies with unit size. Troubleshooting: - Check that the supply voltage matches the frequency converter voltage. - Perform an input voltage test.
ALARM 8 DC under voltage	Cause: If the DC-link voltage (DC) drops below the under voltage limit, the frequency converter trips after a fixed time delay. The time delay varies with unit size. Troubleshooting: - Check that the supply voltage matches the frequency converter voltage. - Perform an input voltage test.
WARNING 9 Inverter overload	Cause: The frequency converter is about to cut out because of an overload (too high current for too long). The counter for electronic, thermal inverter protection issues a warning at 90% and trips at 100%, while issuing an alarm. The frequency converter cannot be reset until the counter is below 90%. - The fault is that the frequency converter is overloaded by more than 100% for too long. Troubleshooting: - Compare the output current shown on the LCP with the frequency converter rated current. - Compare the output current shown on the LCP with measured motor current. - Display the thermal drive load on the LCP and monitor the value. When running above the frequency converter continuous current rating, the counter increases. When running below the frequency converter continuous current rating, the counter decreases.
ALARM 9 Inverter overload	Cause: The frequency converter is about to cut out because of an overload (too high current for too long). The counter for electronic, thermal inverter protection issues a warning at 90% and trips at 100%, while issuing an alarm. The frequency converter cannot be reset until the counter is below 90%. - The fault is that the frequency converter is overloaded by more than 100% for too long. Troubleshooting: - Compare the output current shown on the LCP with the frequency converter rated current. - Compare the output current shown on the LCP with measured motor current. - Display the thermal drive load on the LCP and monitor the value. When running above the frequency converter continuous current rating, the counter increases. When running below the frequency converter continuous current rating, the counter decreases.
WARNING 10 Motor overload temperature	Cause: According to the electronic thermal protection (ETR), the motor is too hot. Select whether the frequency converter issues a warning or an alarm when the counter reaches 100% in parameter 1-90 Motor Thermal Protection. The fault is that the motor is overloaded by more than 100% for too long. Troubleshooting: - Check if the motor is overheating. - Check if the motor is mechanically overloaded - Ensure that the motor parameter 1-24 Motor Current is set correctly. - Ensure motor data in parameters 1-20 through 1-25 are set correctly. - Run AMA in parameter 1-29 Automatic Motor Adaption (AMA).
ALARM 10 Motor overload temperature	Cause: According to the electronic thermal protection (ETR), the motor is too hot. Select whether the frequency converter issues a warning or an alarm when the counter reaches 100% in parameter 1-90 Motor Thermal Protection. The fault is that the motor is overloaded by more than 100% for too long. Troubleshooting: - Check if the motor is overheating. - Check if the motor is mechanically overloaded - Ensure that the motor parameter 1-24 Motor Current is set correctly. - Ensure motor data in parameters 1-20 through 1-25 are set correctly. - Run AMA in parameter 1-29 Automatic Motor Adaption (AMA).
WARNING 11 Motor thermistor over temp	Cause: The thermistor or the thermistor connection is disconnected. Select whether the frequency converter issues a warning or an alarm in parameter 1-90 Motor Thermal Protection. Troubleshooting: - Check if the motor is overheating. - Check if the motor is mechanically overloaded. - Ensure that the thermistor is connected correctly. - If using a thermal switch or thermistor, ensure that the programming of parameter 1-93 Thermistor Source matches sensor wiring.
ALARM 11 Motor thermistor over temp	Cause: The thermistor or the thermistor connection is disconnected. Select whether the frequency converter issues a warning or an alarm in parameter 1-90 Motor Thermal Protection. Troubleshooting: - Check if the motor is overheating. - Check if the motor is mechanically overloaded. - Ensure that the thermistor is connected correctly. - If using a thermal switch or thermistor, ensure that the programming of parameter 1-93 Thermistor Source matches sensor wiring.
WARNING 13 Over current	Cause: The inverter peak current limit is exceeded. The warning lasts about 1.5 s, then the frequency converter trips and issues an alarm. Troubleshooting: - This fault may be caused by shock loading or fast acceleration with high inertia loads. - Turn off the frequency converter. Check if the motor shaft can be turned. - Check that the motor size matches the frequency converter. - Incorrect motor data in parameters 1-20 through 1-25.
ALARM 13 Over current	Cause: The inverter peak current limit is exceeded. The warning lasts about 1.5 s, then the frequency converter trips and issues an alarm. Troubleshooting: - This fault may be caused by shock loading or fast acceleration with high inertia loads. - Turn off the frequency converter. Check if the motor shaft can be turned. - Check that the motor size matches the frequency converter. - Incorrect motor data in parameters 1-20 through 1-25.
ALARM 14 Earth (ground) fault	Cause: There is current from the output phases to earth, either in the cable between the frequency converter and the motor or in the motor itself. Troubleshooting: - Remove power to the frequency converter and repair the earth fault. - Check for earth faults in the motor by measuring the resistance to ground of the motor leads and the motor with a megohmmeter.
ALARM 16 Short circuit	Cause: There is short-circuiting in the motor or motor wiring. Solution: Remove power to the frequency converter and repair the short circuit.
WARNING 17 Control word timeout	Cause: There is no communication to the frequency converter. The warning is only active when 8-04 Control Word Timeout Function is NOT set to OFF. - If 8-04 Control Word Timeout Function is set to Stop and Trip, a warning appears and the frequency converter ramps down until it trips, while giving an alarm. 8-03 Control Timeout Time could possibly be increased Troubleshooting: - Check connections on the serial communication cable. - Increase 8-03 Control Word Timeout Time - Check the operation of the communication equipment. - Verify a proper installation based on EMC requirements.
ALARM 17 Control word timeout	Cause: There is no communication to the frequency converter. The warning is only active when 8-04 Control Word Timeout Function is NOT set to OFF. - If 8-04 Control Word Timeout Function is set to Stop and Trip, a warning appears and the frequency converter ramps down until it trips, while giving an alarm. 8-03 Control Timeout Time could possibly be increased Troubleshooting: - Check connections on the serial communication cable. - Increase 8-03 Control Word Timeout Time - Check the operation of the communication equipment. - Verify a proper installation based on EMC requirements.
WARNING 24 Fan fault	Cause: The fan warning function is an extra protection function that checks whether the fan is running/mounted. The fan warning can be disabled in parameter 14-53 Fan Monitor ([0] Disabled). Troubleshooting: - Check fan resistance.
ALARM 24 Fan fault	Cause: The fan warning function is an extra protection function that checks whether the fan is running/mounted. The fan warning can be disabled in parameter 14-53 Fan Monitor ([0] Disabled). Troubleshooting: - Check fan resistance.
ALARM 30 Motor phase U missing	Cause: Motor phase U between the frequency converter and the motor is missing. Solution: Remove power from the frequency converter and check motor phase U.
ALARM 31 Motor phase V missing	Cause: Motor phase V between the frequency converter and the motor is missing. Solution: Remove power from the frequency converter and check motor phase V.
ALARM 32 Motor phase W missing	Cause: Motor phase W between the frequency converter and the motor is missing. Solution: Remove power from the frequency converter and check motor phase W.
ALARM 38 Internal fault	Cause: Internal fault. Troubleshooting: - Cycle power - Check that the option is properly installed - Check for loose or missing wiring - There is an hardware or software issue in drive. Need to repair or replace drive.
ALARM 44 Earth fault II	Cause: There is a discharge from the output phases to ground, either in the cable between the frequency converter and the motor or in the motor itself. Troubleshooting: - Turn off the frequency converter and remove the ground fault. - Measure the resistance to ground of the motor cables and the motor with a megohmmeter to check for a ground fault in the motor.
ALARM 46 Gate drive voltage low	Cause: The supply on the power card is out of range. There are 3 supplies generated by the switch mode power supply (SMPS) on the power card: 24 V, 5 V, and ±18 V. Troubleshooting: - Check the power card.
ALARM 47 24 V supply low	Cause: The 24 V DC is measured on the control card.It occurs when the detected voltage on terminal 12 is lower than 18 V. Check the control card and the load connected.
ALARM 51 AMA check Unom and Inom	Cause: The setting of motor voltage, motor current, and motor power is presumably wrong. Solution: Check the settings.
ALARM 52 AMA low Inom	Cause: The motor current is too low. - Check the settings.
ALARM 53 AMA motor too big	Cause: The motor is too large for the AMA to be performed.
ALARM 54 AMA motor too small	Cause: The motor is too small for the AMA to be performed.
ALARM 55 AMA Parameter out of range	Cause: The parameter values found from the motor are outside the acceptable range.
ALARM 56 AMA interrupted by user	Cause: The AMA is interrupted.
ALARM 57 AMA timeout	Cause: Try to start the AMA again a number of times, until the AMA is performed. Note that repeated runs may heat the motor to a level where the resistance Rs and Rr are increased. In most cases, this is not critical.
ALARM 58 AMA internal fault	Cause: AMA internal fault. Solution: There is an hardware or software issue in drive. Need to repair or replace drive.
WARNING 59 Current limit	Cause: The current is higher than the value in parameter 4-18 Current Limit.
ALARM 60 External interlock	Cause: External interlock has been activated. To resume normal operation, apply 24 V DC to the terminal programmed for external Interlock and reset the frequency converter (via serial communication, digital I/O, or by pressing [Reset]).
ALARM 69 Power card temperature	Cause: The temperature on the power card is either too high or too low. Troubleshooting: - Ensure that the ambient operating temperature is within the limits. - Check if the filters are clogged. - Check the fan operation. - Check the power card.
ALARM 70 Illegal power section configuration	Cause: The control card and power card are incompatible. Contact your supplier with the type code of the unit from the nameplate and the part numbers of the cards to check compatibility.
ALARM 80 Drive initialised to default value	Cause: Parameter settings are initialised to default settings after a manual reset.
ALARM 95 Broken belt	Cause: Torque is below the torque level set for no load, indicating a broken belt. Parameter 22-60 Broken Belt Function is set for alarm. Troubleshooting: - Troubleshoot the system and reset the frequency converter after clearing the fault.
ALARM 126 Motor Rotating	Cause: During AMA start-up, the motor is rotating. It is only valid for PM motor. Troubleshooting: - Check if the motor is rotating before starting the AMA.
WARNING 127 Back EMF too High	Cause: This warning applies to PM motors only. When the back EMF exceeds 90% x Uinvmax (overvoltage threshold) and does not drop to a normal level within 5 s, this warning is reported. The warning remains until the back EMF returns to a normal level.
WARNING 200 Fire Mode	Cause: Fire mode has been activated.
WARNING 202 Fire Mode Limits Exceeded	Cause: Fire Mode has suppressed one or more warranty-voiding alarms.
ALARM 250 New Spare Part	Cause: The power or switch mode supply has been exchanged.
ALARM 251 New Type Code	Cause: The frequency converter has a new type code.
Err 84 LCP comm.	Cause: Lost Communication between the LCP and the frequency converter is lost.
Err 85 Button disabled	Cause: The LCP key is disabled. One of the LCP keys has been disabled in parameter group 0-4* LCP Keypad.
Err 86 LCP copy failed	Cause: Data copy failure. This error occurs when data is copied from frequency converter to LCP, or from LCP to frequency converter (parameter 0-50 LCP Copy).
Err 88 Data not compatible	Cause: LCP data incompatible. This error occurs when data is being copied from LCP to frequency converter (parameter 0-50 LCP Copy). The typical reason is that data is moved between frequency converter and LCP that have major software differences.
Err 89 Read only	Cause: Parameter read only. An operation is issued via LCP to write a value to a parameter that is read-only.
Err 90 Database busy	Cause: The parameter database of the frequency converter is busy.
Err 91 Parameter invalid	Cause: The parameter value that is input via the LCP is invalid.
Err 92 Exceeds limits	Cause: The parameter value that is input via the LCP exceeds limits.
Err 93 Motor is running	Cause: The LCP copy operation cannot be performed when the frequency converter is running.
Err 95 Not while running	Cause: The parameter cannot be changed while the frequency converter is running.
Err 96 Password rejected	Cause: The password that is input via the LCP is incorrect.
Alarm 50 AMA calibration failed	Cause: AMA calibration  failed
Warning 66 Heat sink temperature low	Cause: Heat sink temperature low.
Warning 79 Illegal PS config	Cause: Illegal PS config.
alarm 79 Illegal PS config	Cause: Illegal PS config.
ALARM 84	Cause:  LCP error
warning 87 Auto DC brake	Cause: Auto DC brake.
WARNING 200 Fire Mode	Cause: Fire mode has been activated.

How to Read FC 101 Faults via LCP & MCT 10

Unlike the FC 102 which usually has a graphical screen, the FC 101 often uses a simpler numeric or alpha-numeric display. Diagnostics in 2026 rely on identifying the specific LCP type:

• LCP 11 / 12 Control Panels:
  • The FC 101 typically uses the LCP 11 (Numeric) or LCP 12 (Alpha-Numeric) panel.
  • Status: An Alarm will cause the display to flash the code number and the Red LED to flash. A Warning will illuminate the Yellow LED.
• MCT 10 Set-up Software: For detailed history, connect a PC via USB. Navigate to Parameter 15-30 (Alarm Log: Error Code). This allows you to view the sequence of faults, which is helpful if a “Mains Phase Loss” caused a subsequent “Undervoltage” trip.
• Fire Mode Status: If the drive is in Fire Mode (open loop smoke extraction), the display may show a status message rather than a fault, as standard protections are disabled to keep the fan running.

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Frequently Asked Questions (FAQ)

Q: What is the difference between the FC 101 and FC 102?

A:

• FC 101 (HVAC Basic): A streamlined drive for simple fans/pumps. It has fewer I/O points and typically comes with a numeric display.
• FC 102 (HVAC Drive): The premium drive with advanced logic, full BMS integration, and a large graphical display.
• Note: Fault codes are largely similar, but the FC 101 lacks some of the advanced application-specific alarms found in the FC 102.

Q: How do I reset a Danfoss FC 101 fault?

A:

1. Press the Reset / Off/Reset button on the keypad.
2. Toggle the Digital Input configured for Reset (Default is Terminal 18 or 19).
3. Trip Lock: If the fault is severe (Ground Fault, Short Circuit), you must cycle the main power (turn off, wait for display to go blank, turn on) to reset the unit.

Q: Why does the drive trip on “Alarm 13” (Overcurrent)?

A: This implies the motor is drawing more amps than the drive allows.

• Check if the fan belt is too tight or the pump impeller is clogged.
• Verify the Ramp Up Time (Parameter 3-41) is not too short.
• Perform an AMA (Automatic Motor Adaptation) via Parameter 1-29 to ensure the drive measures the motor resistance correctly.