Danfoss VLT HVAC Drive FC 102
Danfoss VLT HVAC Drive FC 102 code 4: Mains phase loss
The drive has a missing supply phase or high voltage imbalance, causing the motor to stop.
- Code
- 4
- Name
- Mains phase loss
- Controller
- Danfoss VLT HVAC Drive FC 102
- Type
- Power supply
- What it does
- Fault: the equipment trips and stops
- Risk
- YELLOW Booth plays by its own rules
- Source
- The manufacturer's manual (subscribers see which manual and page)
Updated November 4, 2026
How to fix it
Subscribers get:
- What to do next, in plain words
- What the manual says to do, and the page it is on
- The 3 common causes listed for this code
- Booking a live video call with Ben, a master booth technician ($250/hr, paid per call)
Questions about this code
What does Danfoss VLT HVAC Drive FC 102 code 4 mean?
The drive has a missing supply phase or high voltage imbalance, causing the motor to stop.
Is Danfoss VLT HVAC Drive FC 102 code 4 dangerous?
It is graded yellow: not hard, but a booth does it differently than the gear most techs know, so follow the checks in order.
How do I fix Danfoss VLT HVAC Drive FC 102 code 4?
The manual's fix and the step by step check for this code are in WERCS Diagnose, plans from $49 a month. For help right now, WERCS answers 24/7 at (877) 489-3727.
Other Danfoss VLT HVAC Drive FC 102 codes
1 · 10 Volts low2 · Live zero error5 · DC link voltage high6 · DC link voltage low7 · DC overvoltage8 · DC undervoltage9 · Inverter overload10 · Motor overload temperature
All 73 Danfoss VLT HVAC Drive FC 102 codes · Every fault code