J8 on a Mitsubishi Electric heat pump: Communication failure between wireless receiver and wireless remote controller (address 8)
Short answer
On a Mitsubishi Electric heat pump, J8 means: Communication failure between wireless receiver and wireless remote controller (address 8). The heat pump keeps running with some functions stopped. 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 Ecodan
The manual says: Communication failure between wireless receiver and wireless remote controller (address 8).
Part involved: Wireless remote controller address 8 (PAR-WT50R-E) / receiver.
When it shows: Receiver gets no/incomplete data from wireless remote controller for 15 consecutive minutes; the digit is the controller address.
Likely causes:
- 1 Wireless remote controller battery flat; 2 Controller out of range of receiver; 3 Controller transmission circuit fault; 4 Receiver reception circuit fault.
On the Ecodan Co2 Quhz
The manual says: Wireless remote controller (address 8)/wireless receiver communication failure.
Part involved: Wireless remote controller address 8.
When it shows: No/incomplete data from wireless remote controller for 15 consecutive minutes.
Likely causes:
- Battery flat; controller out of range; controller or receiver board fault.
Is it safe?
On the Ecodan
| Does the heat pump stop? | Partly |
|---|---|
| Severity | Warning |
| Engineer needed? | Yes |
The heat pump keeps running with some functions stopped.
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.
On the Ecodan Co2 Quhz
| Does the heat pump stop? | Partly |
|---|---|
| Severity | Warning |
| Engineer needed? | Yes |
The heat pump keeps running with some functions stopped.
Resetting itself: Not stated as auto-recovering.
Manual reset: Press F4 (Reset) then F3 (Yes) on the main remote controller, or switch system off (installation manual).
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. For a wireless room controller, check/replace its batteries (user-replaceable per the wireless controller manual) and make sure it is within range.
What the engineer will check
On the Ecodan
- 1 Replace batteries; 2-4 Move controller closer and run communication test (OK = range issue; Err = replace controller and re-pair; if still Err replace receiver).
Who to ask for: Mitsubishi Ecodan-trained heat pump engineer (controls / wiring).
On the Ecodan Co2 Quhz
- Replace battery; run communication test; replace controller/receiver as indicated.
Who to ask for: Mitsubishi Ecodan-trained heat pump engineer (controls / wiring).
What you might notice
What owners and engineers report
23 owner and engineer reports mention this.
- Controller / thermostat problem on the Ecodan: 14 reports
- No heating on the Ecodan: 9 reports
Sources
- Ecodan EHPT20X-MEHEW Service Manual (OCH814A) ↗ · OCH814A · page 64 (10-4 Self-diagnosis and action) · Reviewed 23 September 2026
- Ecodan EHPT20Q VM2EA Service Manual (GCH15010C) ↗ · GCH15010C · page 41 (10-4 Self diagnosis and action) · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026