Danfoss VLT 8000 Drive Fault Codes List
Access the complete reference guide for legacy Danfoss VLT 8000 AQUA drive fault codes. Learn to diagnose Alarm 14, Alarm 37, and perform troubleshooting via MCT 10.
Danfoss VLT 8000 Fault Codes Reference Table
Danfoss VLT 8000 Fault Codes Reference Table
VLT® 8000 AQUA Faults and Alarms
| Fault Code and Meaning | Cause and Remedy |
|---|---|
| WARNING 1 Under 10 V (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:
|
| WARNING/ALARM 2 Live zero fault (LIVE ZERO ERROR) |
Cause: The current or voltage signal on terminal 53, 54 or 60 is below 50% of the value preset in parameter 309, 312 and 315 (Terminal, min. scaling). |
| WARNING/ALARM 4 Mains imbalance (MAINS IMBALANCE) |
Cause: High imbalance or phase missing on the supply side.
Remedy:
|
| WARNING 5 Voltage warning high (DC LINK VOLTAGE HIGH) |
Cause: The intermediate circuit voltage (DC) is higher than the Voltage warning high limit. The controls of the frequency converter are still enabled. |
| WARNING 6 Voltage warning low (DC LINK VOLTAGE LOW) |
Cause: The intermediate circuit voltage (DC) is lower than the Voltage warning low limit. The controls of the frequency converter are still enabled. |
| WARNING/ALARM 7 Overvoltage (DC LINK OVERVOLT) |
Cause: The intermediate circuit voltage (DC) is higher than the Overvoltage limit of the inverter. The frequency converter will trip after a fixed period.
Remedy:
|
| WARNING/ALARM 8 Undervoltage (DC LINK UNDERVOLT) |
Cause: The intermediate circuit voltage (DC) drops below the undervoltage limit of the inverter. The frequency converter will trip after a fixed period.
Remedy:
|
| WARNING/ALARM 9 Inverter overload (INVERTER TIME) |
Cause: The electronic, thermal inverter protection reports that the AFD is about to cut out because of an overload (too high current for too long).
Details:
|
| WARNING/ALARM 10 Motor overtemperature (MOTOR TIME) |
Cause: According to the electronic thermal protection (ETR), the motor is too hot. The motor is overloaded by more than 100% of the preset rated motor current for too long.
Remedy:
|
| WARNING/ALARM 11 Motor thermistor (MOTOR THERMISTOR) |
Cause: The thermistor or the thermistor connection has been disconnected.
Remedy:
|
| WARNING/ALARM 12 Current limit (CURRENT LIMIT) |
Cause: The current is higher than the value in parameter 215 (Current limit ILIM). The converter trips after the time set in parameter 412 has passed. |
| WARNING/ALARM 13 Overcurrent (OVER CURRENT) |
Cause: The inverter peak current limit (approx. 200% of the rated current) has been exceeded.
Remedy:
|
| ALARM 14 Ground fault (GROUND FAULT) |
Cause: There is a discharge from the output phases to ground, either in the cable between the AFD and the motor or in the motor itself.
Remedy:
|
| ALARM 15 Switch mode fault (SWITCH MODE FAULT) |
Cause: Fault in the switch mode power supply (internal ± 15 V supply).
Remedy:
|
| ALARM 16 Short-circuiting (CURR. SHORT CIRCUIT) |
Cause: There is short-circuiting on the motor terminals or in the motor itself.
Remedy:
|
| WARNING/ALARM 17 Serial communication timeout (STD BUSTIMEOUT) |
Cause: There is no serial communication with the frequency converter.
Remedy:
|
| WARNING/ALARM 18 HPFB bus timeout (HPFB TIMEOUT) |
Cause: There is no serial communication with the communication option card of the frequency converter.
Remedy:
|
| WARNING 19 Fault in the EEprom on the power card (EE ERROR POWER) |
Cause: There is a fault on the power card EEPROM. The frequency converter will continue to function, but is likely to fail at the next power-up.
Remedy:
|
| WARNING 20 Fault in the EEprom on the control card (EE ERROR CONTROL) |
Cause: There is a fault in the EEPROM on the control card. The frequency converter will continue to function, but is likely to fail at the next power-up.
Remedy:
|
| ALARM 22 Auto-optimisation not OK (AMA FAULT) |
Cause: A fault has been found during automatic motor adaptation. The display indicates the specific sub-code:
CHECK 103, 105 [0] Parameter 103 or 105 has a wrong setting. Correct setting and restart AMA. LOW P.105 [1] Motor is too small for AMA. Param 105 must be > 35% of rated output current. ASYMMETRICAL IMPEDANCE [2] Asymmetrical impedance detected in motor system. Motor could be defective. MOTOR TOO BIG [3] Motor is too big for AMA to be carried out. Check setting in parameter 102. MOTOR TOO SMALL [4] Motor is too small for AMA to be carried out. Check setting in parameter 102. TIME OUT [5] AMA fails because of noisy measuring signals. Try starting AMA again. Note: Repeated AMA runs may heat motor. INTERRUPTED BY USER [6] AMA has been interrupted by the user. INTERNAL FAULT [7] Internal fault in frequency converter. Contact Danfoss supplier. LIMIT VALUE FAULT [8] Parameter values found for the motor are outside acceptable range. MOTOR ROTATES [9] The motor shaft rotates. Ensure load cannot make motor rotate, then restart AMA. |
| ALARM 29 Heat sink temperature too high (HEAT SINK OVER TEMP.) |
Cause: The cut-out temperature of the heat-sink has been reached (90°C or 80°C depending on enclosure).
Remedy: The fault could be the following:
|
| ALARM 30 Motor phase U missing (MISSING MOT.PHASE U) |
Cause: Motor phase U between frequency converter and motor is missing.
Remedy:
|
| ALARM: 31 Motor phase V missing (MISSING MOT.PHASE V) |
Cause: Motor phase V between frequency converter and motor is missing. Remedy:
|
| ALARM: 32 Motor phase W missing (MISSING MOT.PHASE U) |
Cause: Motor phase W between frequency converter and motor is missing. Remedy:
|
| WARNING/ALARM: 34 HPFB communication fault (HPFB COMM. FAULT) |
Cause: The serial communication on the communication option card is not working. |
| ALARM: 37 Inverter fault (GATE DRIVE FAULT) |
Cause: IGBT or the power card is defective. Remedy:
|
| WARNING: 39 CHECK PAR. 104, 106 |
Cause: Parameters 104 Motor frequency fM,N, or 106 Rated motor speed nM,N, have probably not been set correctly. Remedy:
|
| WARNING: 40 CHECK PAR. 103, 105 |
Cause: Parameter 103 Motor voltage, UM,N or 105 Motor current, IM,N has not been set correctly. Remedy:
|
| WARNING: 41 MOTOR TOO BIG (MOTOR TOO BIG) |
Cause: The motor used is probably too big for AMA to be carried out. The setting in parameter 102 Motor power, PM,N may not match the motor. Remedy:
|
| WARNING: 42 MOTOR TOO SMALL (MOTOR TOO SMALL) |
Cause: The motor used is probably too small for AMA to be carried out. The setting in parameter 102 Motor power, PM,N may not match the motor. Remedy:
|
| ALARM: 60 Safety stop (EXTERNAL FAULT) |
Cause: Terminal 27 (parameter 304 Digital inputs) has been programmed for a Safety interlock [3] and is a logic "0". |
| WARNING: 61 Output frequency low (FOUT < FLOW) |
Cause: The output frequency is lower than parameter 223 Warning: Low frequency, fLOW. |
| WARNING: 62 Output frequency high (FOUT > FHIGH) |
Cause: The output frequency is higher than parameter 224 Warning: High frequency, fHIGH. |
| WARNING/ALARM: 63 Output current low (I MOTOR < I LOW) |
Cause: The output current is lower than parameter 221 Warning: Low current, ILOW. Remedy:
|
| WARNING: 64 Output current high (I MOTOR > I HIGH) |
Cause: The output current is higher than parameter 222 Warning: High current, IHIGH. |
| WARNING: 65 Feedback low (FEEDBACK < FDB LOW) |
Cause: The resulting feedback value is lower than parameter 227 Warning: Low feedback, FBLOW. |
| WARNING: 66 Feedback high (FEEDBACK > FDB HIGH) |
Cause: The resulting feedback value is higher than parameter 228 Warning: High feedback, FBHIGH. |
| WARNING: 67 Remote reference low (REF. < REF LOW) |
Cause: The remote reference is lower than parameter 225 Warning: Low reference, REFLOW. |
| WARNING: 68 Remote reference high (REF. > REF HIGH) |
Cause: The remote reference is higher than parameter 226 Warning:High reference, REFHIGH. |
| WARNING: 69 Temperature auto derate (TEMP.AUTO DERATE) |
Cause: The heat sink temperature has exceeded the maximum value and the auto derating function (par. 411) is active. |
| WARNING: 99 Unknown fault (UNKNOWN ALARM) |
Cause: An unknown fault has occurred that cannot be processed by the software. Remedy:
|
How to Read VLT 8000 Faults via LCP & MCT 10
Diagnosing the VLT 8000 in 2026 often requires bridging the gap between old hardware and new software. Here is how to access critical data:
- Local Control Panel (LCP): The VLT 8000 features a 4-line alphanumeric display.
- Extended Status: Press the [DISPLAY / STATUS] button to cycle through readouts. If the drive trips on “Alarm 14” (Earth Fault), check the status line to see if it occurred during ramp-up or steady run.
- Log: The log history is accessible via Parameter 600-605, storing the last few fault events.
- MCT 10 Set-up Software: Even though the drive is obsolete, modern MCT 10 software still supports it.
- Connection: You cannot use USB directly. You must use a USB-to-RS485 converter connected to terminals 68 (+) and 69 (-).
- Scope: Once connected, you can view parameter backups and the alarm log to determine if the drive parameters have drifted or been tampered with over the years.
Frequently Asked Questions (FAQ)
Q: What is the difference between a Warning and an Alarm on the VLT 8000?
A:
- Warning (W): The drive detects a problem (e.g., “Warning 37” Communication Error) but keeps the pump running to ensure water pressure is maintained.
- Alarm (AL): The drive trips immediately to protect the internal IGBTs (e.g., “Alarm 13” Overcurrent). A manual reset is required.
Q: How do I reset a Danfoss VLT 8000 fault?
A:
- Press the [RESET] button on the LCP.
- Toggle the Digital Input configured for Reset (Terminal 19 is the default).
- Power cycle the drive (Wait at least 30 seconds for the DC bus to discharge).
Q: My spare VLT 8000 blew up upon installation. Why?
A: Capacitor Aging. If a VLT 8000 has been sitting on a shelf as a spare for more than 2-3 years, the electrolytic capacitors have dried out. Applying full power immediately can cause them to explode. You must “reform” the capacitors by applying voltage gradually over several hours using a variac.
Q: What is the modern replacement for the VLT 8000?
A: The direct successor is the Danfoss VLT AQUA Drive FC 202. It offers higher efficiency, native cascade control, and backward compatibility with VLT 8000 parameter logic (with some conversion).
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