Danfoss VLT HVAC Drive FC 102
Danfoss VLT HVAC Drive FC 102 code 34: Fieldbus communication fault
The drive loses network control because the serial communication bus on the option card is not working.
- Code
- 34
- Name
- Fieldbus communication fault
- Controller
- Danfoss VLT HVAC Drive FC 102
- Type
- Communication
- 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
- Which manufacturer manual it comes from, linked
- The step by step check for this problem, one check at a time
- 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 34 mean?
The drive loses network control because the serial communication bus on the option card is not working.
Is Danfoss VLT HVAC Drive FC 102 code 34 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 34?
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
30 · Motor phase U missing31 · Motor phase V missing32 · Motor phase W missing33 · Inrush fault36 · Mains failure38 · Internal fault39 · Heatsink sensor40 · Overload of digital output terminal 2741 · Overload of digital output terminal 2942 · Overload of digital output on X30/6 or o
All 73 Danfoss VLT HVAC Drive FC 102 codes · Every fault code