com-error-exv-card on a Thermia Atec: Communication broken between display card and expansion valve control card (outdoor)
Short answer
On a Thermia heat pump, com-error-exv-card means: Communication broken between display card and expansion valve control card (outdoor). The heat pump stops until the fault clears or is reset. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Communication broken between display card and expansion valve control card (outdoor).
Part involved: EXV control card.
Likely causes:
- Communication cable/connection or card fault. (causes from the equivalent Danfoss DHP-AQ service instructions VMGFJ202).
Is it safe?
| Does the heat pump stop? | Yes |
|---|---|
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Manual reset: Set operating mode OFF then back to the desired mode.
What you can check
- Note the exact alarm text. Acknowledge once (operating mode OFF then back); if it remains, contact a service technician (user manual 086L0130 p.25).
What the engineer will check
- Check/replace communication cable; test EXV card.
Who to ask for: heat pump engineer.
Certification: Qualified electrician / heat pump engineer (electrical fault-finding).
What you might notice
Sources
- Service Instructions Atec (VIIFM102) - silo.tips copy ↗ · VIIFM102 · page p.10-11 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026