F.718 on a Vaillant heat pump: Fan unit 1: Fan blocked
Short answer
On a Vaillant heat pump, F.718 means: Fan unit 1: Fan blocked. The heat pump stops until the fault clears or is reset. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 2 sources
What it means
On the aroTHERM plus (VWL ../6 A)
The manual says: Fan unit 1: Fan blocked.
Part involved: Fan blocked.
When it shows: No feedback signal that fan 1 is rotating; preceded by status S.252 (fan restarted after 15 min, up to four attempts).
Likely causes:
- There is no confirmation signal stating that the fan is rotating.
On the flexoTHERM exclusive (VWF ../4)
The manual says: Fan unit 1: Fan blocked.
Part involved: Fan blocked.
Likely causes:
- There is no confirmation signal stating that the fan is rotating.
Is it safe?
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Fault — needs a manual reset once the cause is fixed |
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Resetting itself: no - the fault remains displayed until the cause is eliminated.
Manual reset: yes - after the cause is eliminated, press the reset button (indoor unit) or reset via the system control; if it recurs after several resets contact customer service.
What you can check
On the aroTHERM plus (VWL ../6 A)
- Note the full code and text shown on the display (and the date/time it appeared). Check the outdoor unit's air inlet and outlet are not blocked by leaves, debris, snow or ice build-up and clear any loose debris from around it (do not open the casing, poke the fins or use tools). The operating instructions allow the reset button on the indoor unit (or a reset via the system control) to be pressed once; if the code returns, do not keep resetting - contact your installer or Vaillant.
On the flexoTHERM exclusive (VWF ../4)
- Note the full code and text shown on the display (and the date/time it appeared). Check the outdoor unit's air inlet and outlet are not blocked by leaves, debris, snow or ice build-up and clear any loose debris from around it (do not open the casing, poke the fins or use tools). Do not keep resetting the unit; report the code to your installer (the operating instructions for this product were not checked for a homeowner reset procedure).
What the engineer will check
On the aroTHERM plus (VWL ../6 A)
- Check the air route and, if required, remove any blockages.
Who to ask for: Vaillant-trained heat pump installer/engineer (MCS-certified installer).
Certification: MCS installer certification; Vaillant product training recommended.
On the flexoTHERM exclusive (VWF ../4)
- Check the air route and, if required, remove any blockages; Check and, if required, replace the F1 fuse on the PCB in the fan unit (OMU).
Who to ask for: Vaillant-trained heat pump installer/engineer (MCS-certified installer).
Certification: MCS installer certification; Vaillant product training recommended.
What you might notice
What owners and engineers report
8 owner and engineer reports mention this.
- No heating on the aroTHERM plus (VWL ../6 A): 8 reports
Sources
- Heat pump control interface module (VWZ AI) operating and installation instructions ↗ · 0020291573_01 · page VWZ AI appliance interface 0020291573_01 p.34; uniTOWER VIH QW 190/6 E 0020291525_05 p.60; aroTHERM split hydraulic station VWL ../5 IS 0020257319_05 p.57 · Reviewed 23 September 2026
- flexoTHERM exclusive VWF 57/4 - 197/4 400V installation and maintenance instructions ↗ · 0020213394_05 · page flexoTHERM 400 V 0020213394_05 p.52; flexoTHERM 230 V 0020213395_04 p.47 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026