09 on a Viessmann Vitotronic 200: Short circuit/lead break evaporator temperature sensor
Short answer
On a Viessmann heat pump, 09 means: Short circuit/lead break evaporator temperature sensor. The manual does not say whether the heat pump stops. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manuals for this range word it in different ways:
- Short circuit/lead break evaporator temperature sensor.
- Short circuit/lead break, defrost temperature sensor.
- Electricity meter PV: Utilisation of PV power generated on site not possible.
Part involved: Short circuit/lead break evaporator temperature sensor; Short circuit/lead break, defrost temperature sensor; Electricity meter PV.
When it shows: Type "Fault" (S) - triggers "05 Refrigerant circuit" on the heat pump control unit. Heat pump characteristics: Compressor may stop due to a change in refrigerant circuit conditions. Type "Fault" (S) - triggers "05 Refrigerant circuit" on the heat pump control unit. Heat pump characteristics: Cooling mode:; Compressor remains in operation. Heating mode:; Compressor OFF Utilisation of PV power generated on site not possible.
Likely causes:
- Short circuit/lead break evaporator temperature sensor.
- Short circuit/lead break, defrost temperature sensor.
- code Phase 1 Phase 2 Phase 3 "01" X "02" X "03" X X "04" X "05" X X "06" X X "07" X X ….
Is it safe?
| Does the heat pump stop? | Not stated |
|---|---|
| Engineer needed? | Yes |
The manual does not say whether the heat pump stops.
Resetting itself: Not stated in 6150133.
Manual reset: Refrigerant circuit messages cannot be acknowledged in the message history (6150133 p.155); acknowledge the resulting 05/07/A9 message on the control unit.
What you can check
- This code is only visible to engineers in the service menu (Diagnosis > Refrigerant circuit > Message history); homeowners see message 05, 07 or A9 - note that code and call your contractor.
- Note the 2-character message code and message text shown on the Vitotronic 200 display (press OK for details) and give them to your heating contractor (operating instructions 5817913 p.56).
- You may acknowledge the message once with OK as described in the Vitotronic 200 operating instructions; if it reappears, do not keep acknowledging it - call your contractor.
- Check the heat pump breaker/isolator in the consumer unit is ON (do not repeatedly reset a breaker or RCD that keeps tripping).
What the engineer will check
- Check resistance value (Pt500A) at the sensor connection of the EEV PCB: See "EEV PCB [2] ".
- Check resistance value (NTC 20 k) Ω at connection T-SENSOR2 on the main PCB: See "Main PCB [7] / [7-1] ".
- Have electricity meter checked by an electrical engineer.
Who to ask for: Viessmann-trained heat pump engineer with F-gas refrigeration certification; Viessmann-trained heat pump engineer / qualified electrician.
Certification: F-gas certificate (UK F-gas Regulations; Viessmann: refrigerant work by authorised refrigeration engineers only); Qualified electrician for work on electrical equipment (Viessmann safety instructions).
What you might notice
Sources
- Service instructions Vitotronic 200 type WO1C heat pump control unit (air/water split & monobloc, brine/water) (6150133, 2023-07) ↗ · 6150133 VSA00004 · pages 156, 183, 86 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026