FB on a Mitsubishi Electric Ecodan: FTC2 unit control system error (memory error, etc.)
Short answer
On a Mitsubishi Electric heat pump, FB means: FTC2 unit control system error (memory error, etc.). 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: FTC2 unit control system error (memory error, etc.).
Part involved: FTC2 control board.
When it shows: Control system / memory error on FTC2 board.
Likely causes:
- FTC2 board memory/control fault.
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: Not stated as auto-resetting; code remains until reset.
Manual reset: Installation manuals: press F4 (RESET) then F3 (Yes) on the main remote controller (older controllers: hold button E for 3 s); 'To cancel error codes please switch system off'. Fix the cause first.
What you can check
- Note the code, unit and ref. address shown on the main remote controller and contact your installer (Mitsubishi user manuals: 'Make a note of the error code number and contact installer'). Check the heat pump breaker/isolator at the consumer unit is on and read the primary system pressure gauge (if fitted) so you can report it. A single reset from the main remote controller (RESET, then Yes) may be tried; if the code returns, do not keep resetting. Do not open the outdoor unit, cylinder/hydrobox or any casing.
What the engineer will check
- Power-cycle; replace FTC2 control board if it persists.
Who to ask for: Mitsubishi Ecodan-trained heat pump engineer (controls / wiring).
Certification: Competent electrician (BS 7671 / Part P); heat pump inverter experience.
What you might notice
What owners and engineers report
16 owner and engineer reports mention this.
- Controller / thermostat problem on the Ecodan: 14 reports
- Heat pump will not start on the Ecodan: 2 reports
Sources
- Ecodan PAC-IF031B-E Installation Manual ↗ · PAC-IF031B-E installation manual · page 21 (7-2 Self-check) · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026