07 on a Stiebel Eltron heat pump: Exhaust air fan: The fan is blocked. The heat pump will be locked out
Short answer
On a Stiebel Eltron heat pump, 07 means: Exhaust air fan: The fan is blocked. The heat pump will be locked out. The heat pump stops until the fault clears or is reset. An engineer is needed to fix the cause. The wording differs by model range — each is shown below.
Reviewed 23 September 2026 · 2 sources
What it means
On the LWZ 5/8 CS Premium, LWZ 5 S Plus, LWZ 5/8 S Trend, LWZ 5 S Smart (integral ventilation units)
The manual says: Exhaust air fan: The fan is blocked. The heat pump will be locked out.
Part involved: fans / ventilation sensors.
When it shows: The fan is blocked. The heat pump will be locked out.
Likely causes:
- Fan switched on but no feedback to the PCB; fan fuse blown; or utility power-off with POWER-OFF parameter set incorrectly. (Also shown during screed drying when compressor MCBs are off.).
On the LWZ 304 SOL / LWZ 404 SOL (integral ventilation units)
The manual says: Exhaust air fan: Fan speed not correct; fan and heat pump are blocked.
Part involved: fans / ventilation sensors.
When it shows: Fan speed not correct; fan and heat pump are blocked.
Is it safe?
On the LWZ 5/8 CS Premium, LWZ 5 S Plus, LWZ 5/8 S Trend, LWZ 5 S Smart (integral ventilation units)
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Warning |
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Resetting itself: no.
Manual reset: electronics reset button / STB reset per manual.
On the LWZ 304 SOL / LWZ 404 SOL (integral ventilation units)
| Does the heat pump stop? | Yes |
|---|---|
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Resetting itself: unknown.
Manual reset: unknown.
What you can check
- Note the fault number shown on the programming unit display.
- Check the appliance breakers/MCBs at the consumer unit are on.
What the engineer will check
On the LWZ 5/8 CS Premium, LWZ 5 S Plus, LWZ 5/8 S Trend, LWZ 5 S Smart (integral ventilation units)
- Isolate across all poles for approx. one minute; check power-OFF contact/parameter; press electronics reset. If the fan repeatedly fails to start, inform your qualified contractor.
Who to ask for: MVHR/ventilation-competent heat pump engineer.
On the LWZ 304 SOL / LWZ 404 SOL (integral ventilation units)
- Follow remedy in LWZ 304/404 SOL installation manual section 9.4; causes largely parallel LWZ 5-8 list.
Who to ask for: MVHR/ventilation-competent heat pump engineer.
What you might notice
Sources
- COMMISSIONING AND NOTIFICATION LIST LWZ 8 CS Premium / LWZ 5 CS Premium / LWZ 5 S Plus / LWZ 8 CS Trend / LWZ 8 S Trend / LWZ 5 S Trend / LWZ 5 S Smart (doc-00081766) ↗ · A 338916-45679-9862 · page 17 · Reviewed 23 September 2026
- INSTALLATION LWZ 304 SOL / LWZ 404 SOL (English, via ManualsLib manual 1279865) ↗ · page 42 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026