Danfoss VLT HVAC Drive FC 102
Danfoss VLT HVAC Drive FC 102 code 66: Heatsink temperature low
The drive will not operate because the heatsink temperature sensor indicates the unit is too cold.
- Code
- 66
- Name
- Heatsink temperature low
- Controller
- Danfoss VLT HVAC Drive FC 102
- Type
- Under temperature
- What it does
- Warning: the equipment keeps running and flags a problem
- Risk
- GREEN In your wheelhouse
- Source
- The manufacturer's manual (subscribers see which manual and page)
Updated November 4, 2026
How to fix it
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- What to do next, in plain words
- What the manual says to do, and the page it is on
- The step by step check for this problem, one check at a time
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Questions about this code
What does Danfoss VLT HVAC Drive FC 102 code 66 mean?
The drive will not operate because the heatsink temperature sensor indicates the unit is too cold.
Is Danfoss VLT HVAC Drive FC 102 code 66 dangerous?
It is graded green: in a working tech's wheelhouse with standard tools and low risk.
How do I fix Danfoss VLT HVAC Drive FC 102 code 66?
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
59 · Current limit60 · External interlock62 · Output frequency at maximum limit65 · Control card overtemperature67 · Option module configuration has changed68 · Safe Stop activated69 · Power card temperature70 · Illegal FC configuration80 · Drive initialized to default value92 · No-Flow
All 73 Danfoss VLT HVAC Drive FC 102 codes · Every fault code