Danfoss VLT 6000 Drive Fault Codes List

Access the complete 2026 reference guide for legacy Danfoss VLT 6000 HVAC fault codes. Learn to diagnose Alarm 14, connect MCT 10 via RS-485, and plan retrofits to the FC 102.

Danfoss VLT 6000 Fault Codes Reference Table

Danfoss VLT Warnings and Alarms

Fault Code and Meaning	Cause and Remedy
WARNING 1 10 VOLT LOW	Cause: The 10 V voltage from terminal 50 on the control card is below 10 V. The 10 volts supply is overloaded. Remedy: Remove some of the load from terminal 50. Ensure load does not exceed 17 mA (minimum resistance is 590 Ω).
WARNING/ALARM 2 LIVE ZERO ERROR	Cause: The current or voltage signal on terminal 53, 54 or 60 is below 50% of the value preset in parameters 309, 312 and 315 (Terminal, Minimum Scaling).
WARNING/ALARM 4 MAINS PHASE LOSS	Cause: Phase missing on the input power. Remedy: Check the supply voltage to the drive.
WARNING 5 DC LINK VOLTAGE HIGH	Cause: The intermediate DC circuit voltage is higher than Voltage Warning High. The drive is still controlling the motor.
WARNING 6 DC LINK VOLTAGE LOW	Cause: The intermediate DC circuit voltage is lower than Voltage Warning Low. The drive is still controlling the motor.
WARNING/ALARM 7 DC LINK OVERVOLT	Cause: The intermediate circuit voltage (DC) is higher than the Overvoltage Limit of the drive. The drive will trip after a fixed period (depends upon the unit).
WARNING/ALARM 8 UNDERVOLTAGE (DC LINK UNDERVOLT)	Cause: The intermediate circuit voltage (DC) drops below the Undervoltage Limit of the inverter. The drive will trip after a fixed period. Remedy: Check whether the supply voltage matches the drive rating.
WARNING/ALARM 9 INVERTER TIME	Cause: The electronic thermal inverter protection reports that the drive is about to trip because of an overload (Warning at 98%, Trip at 100%). The drive cannot be reset until counter drops below 90%. Remedy: Activate ASFM (Automatic Switching Frequency Modulation) in parameter 408 (Interference Reduction Method). Reduce the carrier frequency in parameter 407 (Switching Frequency).
WARNING/ALARM 10 MOTOR TIME	Cause: According to the electronic thermal protection, the motor is overheated. The motor is overloaded to more than 100% of the preset rated motor current for too long. Remedy: Check that the motor parameters 102 through 106 have been set correctly.
WARNING/ALARM 11 MOTOR THERMISTOR	Cause: The thermistor or the thermistor connection has been disconnected. Remedy: Check that the thermistor has been correctly connected between terminal 53 or 54 (analog voltage input) and terminal 50 (+10 V supply).
WARNING/ALARM 12 CURRENT LIMIT	Cause: The current is higher than the value in parameter 215 (Current Limit) and the drive trips after the time set in parameter 412 (Trip Delay Overcurrent) has passed. Remedy: Run AMA on a cold motor in parameter 107 (Automatic Motor Adaptation).
WARNING/ALARM 13 OVER CURRENT	Cause: The inverter peak current limit (approx 200% of rated current) has been exceeded. Remedy: Turn off the drive and check for free rotation of the motor shaft. Check for other causes of overload. Run AMA on a cold motor in parameter 107.
ALARM 14 EARTH FAULT	Cause: There is current leakage from the output phases to ground, either in the leads between the drive and the motor or in the motor itself. Remedy: Remove power to the drive and correct the ground fault.
ALARM 15 SWITCH MODE FAULT	Cause: Fault in the switch mode power supply (internal ±15 V supply). Remedy: Contact the Danfoss Graham service department.
ALARM 16 CURR. SHORT CIRCUIT	Cause: There is a short circuit in the output from the drive. Remedy: Remove power to the drive and correct the short circuit.
WARNING/ALARM 17 STD BUSTIMEOUT	Cause: There is no serial communication with the drive. (Only enabled if parameter 510 is not OFF). Remedy: It is possible to increase parameter 509 (Bus Time Interval).
WARNING/ALARM 18 HPFB TIMEOUT	Cause: There is no serial communication with the communication option card in the drive. (Only enabled if parameter 804 is not OFF). Remedy: Parameter 803 (Bus Time Interval) could possibly be increased.
WARNING 19 EE ERROR POWER	Cause: There is a fault on the power card EEPROM. The drive will continue to function, but is likely to fail at the next power-up. Remedy: Contact the Danfoss Graham service department.
WARNING 20 EE ERROR CONTROL	Cause: There is a fault in the EEPROM on the control card. The drive will continue to function, but is likely to fail at the next power-up. Remedy: Contact the Danfoss Graham service department.
ALARM 22 AMA FAULT	Cause: A fault has been found during automatic motor adaptation (AMA). The text shown in the display indicates a fault message. AMA can only be carried out if there are no alarms during the AMA process. Details: CHECK 103, 105: Parameter 103 or 105 has a wrong setting. Correct the setting and repeat AMA. LOW P 105: The motor is too small for AMA to be carried out. If AMA is to be enabled, the rated motor current, parameter 105, must be higher than 35% of the rated output current of the drive. ASYMMETRICAL IMPEDANCE: AMA has detected an asymmetrical impedance in the motor connected to the system. The motor could be defective. MOTOR TOO BIG: The motor connected to the system is too big for AMA to be carried out. The setting in parameter 102 does not match the motor used. MOTOR TOO SMALL: The motor connected to the system is too small for AMA to be carried out. The setting in parameter 102 does not match the motor used. TIME OUT: AMA fails because of noisy measuring signals. Retry until AMA is successfully completed. Please note that repeated AMA runs may heat the motor to a level where the stator resistance is increased. INTERRUPTED BY USER: AMA has been interrupted by the user. INTERNAL FAULT: An internal fault has occurred in the drive. Contact Danfoss Graham service department. LIMIT VALUE FAULT: The parameter values found for the motor are outside the acceptable range within which the drive is able to work. MOTOR ROTATES: The motor shaft is rotating. Make sure that the load is not able to make the motor shaft rotate while the AMA is being performed. Then start AMA all over.
ALARM 29 HEAT SINK OVER TEMP.	Cause: The heatsink temperature became too high. For NEMA 1 drives, the limit is 90°C. For NEMA 12 drives, the limit is 80°C. The tolerance is ±5°C. The fault cannot be reset until the temperature of the heatsink has fallen below 60°C. The fault could be due to the following: Ambient temperature too high Air obstructed Cooling fan(s) not operating Motor leads too long Too high a switching frequency
ALARM 30 MISSING MOT.PHASE U	Cause: Motor phase U, as indicated by the letters on the output terminal block, is missing or has a high impedance. Remedy: Remove power to the drive and check motor phase U.
ALARM 31 MISSING MOT.PHASE V	Cause: Motor phase V, as indicated by the letters on the output terminal block is missing or has a high impedance. Remedy: Remove power to the drive and check motor phase V.
ALARM 32 MISSING MOT.PHASE W	Cause: Motor phase W, as indicated by the letters on the output terminal block is missing or has a high impedance. Remedy: Remove power to the drive and check motor phase W.
WARNING/ALARM 34 HPFB COMM. FAULT	Cause: The serial communication on the communication option card is not working.
WARNING 35 OUT FREQ RNG/ROT LIM	Cause: This warning will occur if the output frequency has reached its Output Frequency Low Limit, parameter 201, or Output Frequency High Limit, parameter 202. If the drive is in Closed Loop, parameter 100, the warning will show in the display.
ALARM 37 GATE DRIVE FAULT	Cause: An output IGBT or the power card is defective. Remedy: Contact the Danfoss Graham service department.
WARNING 39 CHECK PAR. 104, 106	Cause: Parameters 104, Motor Frequency, or 106, Rated Motor Speed, have probably not been set correctly. (Part of Auto Optimization Warnings 39 through 42). Remedy: Correct the setting and run AMA again. A choice must be made by pressing CHANGE DATA and choosing 'Continue' + OK or 'Stop' + OK. If parameters need to be changed, select 'Stop', change the parameters and run AMA again.
WARNING 40 CHECK PAR. 103, 105	Cause: Parameter 103 Motor Voltage, or 105 Motor Current, has not been set correctly. Remedy: Correct the setting and run AMA again. (Follow standard AMA interaction procedure).
WARNING 41 MOTOR TOO BIG	Cause: The motor used is probably too large for AMA to be carried out. The setting in parameter 102 Motor Power, may not match the motor. Remedy: Check the motor and select 'Continue' or [STOP].
WARNING 42 MOTOR TOO SMALL	Cause: The motor used is probably too small for AMA to be carried out. The setting in parameter 102 Motor Power, may not match the motor. Remedy: Check the motor and select 'Continue' or [STOP].
ALARM 60 EXTERNAL FAULT	Cause: Terminal 27, parameter 304, Digital Inputs, has been programmed for a Safety Interlock and is a logic '0'.
WARNING 61 FOUT < FLOW	Cause: The output frequency is lower than parameter 223, Warning: Low Frequency.
WARNING 62 FOUT > FHIGH	Cause: The output frequency is higher than parameter 224, Warning: High Frequency.
WARNING/ALARM 63 I MOTOR < I LOW	Cause: The output current is lower than parameter 221, Warning: Low Current. Remedy: Select the required function in parameter 409, Function in Case of No Load.
WARNING 64 I MOTOR > I HIGH	Cause: The output current is higher than parameter 222, Warning: High Current.
WARNING 65 FEEDBACK < FDB LOW	Cause: The resulting feedback value is lower than parameter 227, Warning: Low Feedback.
WARNING 66 FEEDBACK > FDB HIGH	Cause: The resulting feedback value is higher than parameter 228, Warning: High Feedback.
WARNING 67 REF. < REF LOW	Cause: The remote controlled reference is lower than parameter 225, Warning: Low Reference.
WARNING 68 REF. > REF HIGH	Cause: The remote controlled reference is higher than parameter 226, Warning: High Reference.
WARNING 69 TEMP.AUTO DERATE	Cause: The heat sink temperature has exceeded the maximum value and the auto derating function in parameter 411, Function at Over Temp, is active.
WARNING 99 UNKNOWN ALARM	Cause: An unknown fault has occurred which the software is not able to handle. Remedy: Contact Danfoss Graham service department.

 

How to Read VLT 6000 Faults via LCP & MCT 10

Diagnosing the VLT 6000 in 2026 often requires bridging the gap between old hardware and modern software:

• The LCP (Local Control Panel): The classic alphanumeric display.
  • Alarm (Trip): The drive stops, the “Alarm” LED flashes red, and the code (e.g., Alarm 14) is displayed.
  • Warning: The “Warning” LED flashes yellow. The drive continues to run, but may reduce frequency (e.g., Warning 12 “Current Limit”).
• MCT 10 via RS-485: Unlike modern drives with USB, the VLT 6000 communicates via RS-485 (Terminals 68 and 69). You can still use the modern MCT 10 software to extract fault logs, but you will need a USB-to-RS485 converter to connect your laptop to the drive terminals.
• Capacitor Aging: If you are pulling a VLT 6000 spare off the shelf that has been stored for more than 2 years, do not power it up immediately. The DC bus capacitors must be reformed (voltage applied gradually), or they may explode.

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Frequently Asked Questions (FAQ)

Q: How do I reset a Danfoss VLT 6000 fault?

A:

1. Press the RESET button on the LCP.
2. Toggle the digital input (Terminal 19 is the default reset).
3. Cycle the mains power. Note: For “Trip Locked” faults (like Alarm 13 Overcurrent), mains power must be cycled to clear the lock.

Q: What should I do for “Alarm 14” (Earth Fault)?

A: This is common in aging HVAC installations.

• It indicates current is leaking from the motor output phases to the ground.
• Disconnect the motor cable from the drive and Megger test the motor/cable insulation.
• If the motor tests fine, the current sensor inside the VLT 6000 may have failed due to age.

Q: Can I replace a VLT 6000 with an FC 102?

A: Yes. The Danfoss VLT HVAC Drive FC 102 is the direct successor.

• Danfoss offers retrofit kits that allow the FC 102 to fit into the same physical footprint as the VLT 6000.
• You can use MCT 10 software to convert the VLT 6000 parameter file into an FC 102 file, simplifying the programming.