F12 on a Panasonic heat pump: Pressure switch activate
Short answer
On a Panasonic heat pump, F12 means: Pressure switch activate. 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: Pressure switch activate.
Part involved: Outdoor high pressure switch.
When it shows: During operation of cooling and heating, when pressure 4.5 MPa and above is detected by outdoor high pressure switch. Service-manual table judgement: 4 times occurrence within 30 minutes (L, J MXC); 4 times occurrence within 20 minutes (K, J MDC, J AIO, H, F, E, D5, D8, C).
Likely causes:
- 1 Dust accumulation on the outdoor unit heat exchanger. 2 Air short circuit at outdoor unit. 3 Faulty water pump. 4 Insufficient water flow rate in system. 5 Water leak in system. 6 2/3 way valve closed. 7 Clogged expansion valve or strainer. 8 Excessive refrigerant. 9 Faulty outdoor high pressure sensor and switch. 10 Faulty outdoor unit PCB.
Is it safe?
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Safety lockout |
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Resetting itself: Not stated in the Panasonic documents opened; protection counters lock out after the stated number of occurrences.
Manual reset: User: 'Error Reset' in the remote-controller Quick Menu (H/J/K/L controllers) or OFF/ON; engineer must clear the underlying cause (service manuals: 'When error happens, the power has to be reset').
What you can check
- Read and note the code shown blinking on the remote controller (also stored under System Check > Error history). Per the Panasonic operating instructions the user may switch the system OFF/ON at the remote controller and use 'Error Reset' in the Quick Menu; if the code returns, leave the system and contact the installer (UK user guide lists Panasonic technical support as the fallback). Check from a distance that the outdoor unit air inlet/outlet is not blocked by snow, leaves or other debris (listed in the operating instructions' checks before calling for service); never reach into the fan.
What the engineer will check
- Check outdoor heat exchanger for dust/blockage and air short-circuit; check water flow (pump, flow rate, leaks, closed 2/3-way valves); check expansion valve/strainer; check refrigerant overcharge; check high pressure sensor/switch and outdoor PCB.
Who to ask for: F-gas certified refrigeration / heat pump engineer (Panasonic-trained).
Certification: UK F-gas certification (Category I) for any refrigerant-circuit work; flammable-refrigerant competence for R32 (J/K) and R290 (L/M) units.
What you might notice
Sources
- Service Manual Hydromodule WH-SDC0509L3E5/L6E5 with WH-WDG05LE5/07LE5/09LE5 (Order No PAPAMY2307068CE) ↗ · PAPAMY2307068CE · page 190 (error codes table); 220 (self-diagnosis) · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026