E8 • Mitsubishi Electric
Fault code E8 Mitsubishi Electric: causes, diagnosis and solution
Fault code E8 indicates a communication error (signal reception error) between the indoor unit (Interface unit/Flow temp. controller) and the outdoor unit. This fault is triggered when the outdoor unit receives no normal signal for a period of 3 minutes.
Proof status : Manufacturer reference needed for the exact range
Source: Mitsubishi Electric documentation (service manual – according to product reference)
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Founder of AskMarcel.app. Sheets are written from manufacturer documentation; the reference is shown when it has been verified.
In brief
Fault code E8 on Mitsubishi Electric means: Fault code E8 indicates a communication error (signal reception error) between the indoor unit (Interface unit/Flow temp. controller) and the outdoor unit. This fault is triggered when the outdoor unit receives no normal signal for a period of 3 minutes. Most common cause: The main cause is a communication failure between the units, due either to a poor connection or faulty contact of the cables linking the indoor unit to the outdoor unit, or to electrical noise entering these cables. Another possible cause is a defective communication circuit on the indoor unit controller board or on the outdoor unit controller board. First action: Check for disconnection or loosening of the cable connecting the indoor unit/flow temperature controller to the indoor unit or outdoor unit.. Call a registered engineer if the fault returns after basic checks or involves refrigerant work (F-Gas registered engineer required).
According to Mitsubishi Electric service documentation, fault code E8 is triggered when the outdoor unit controller board receives no normal signal for a continuous period of 3 minutes.
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What does fault code E8 on Mitsubishi Electric mean?
Fault code E8 indicates a communication error (signal reception error) between the indoor unit (Interface unit/Flow temp. controller) and the outdoor unit. This fault is triggered when the outdoor unit receives no normal signal for a period of 3 minutes.
The main cause is a communication failure between the units, due either to a poor connection or faulty contact of the cables linking the indoor unit to the outdoor unit, or to electrical noise entering these cables. Another possible cause is a defective communication circuit on the indoor unit controller board or on the outdoor unit controller board.
Symptoms
- Display of fault code E8 on the indoor unit screen.
- No normal signal reception by the outdoor unit controller board for 3 minutes.
- Loss of communication between the indoor and outdoor units.
- System shutdown or malfunction of the heating/cooling system.
Diagnosis
1. Check connections
- Check for disconnection or loosening of the cable connecting the indoor unit/flow temperature controller to the indoor unit or outdoor unit.
- Visually inspect the communication cables for any physical damage.
2. Reset and replacement test
- Isolate the power supply and then restore it to check if the fault persists.
- If fault code E8 reappears, replace the Interface/Flow temp. controller board or the outdoor unit controller board.
Repair and return to service — Mitsubishi Electric fault E8
Start by checking for disconnection or loose cables between the indoor and outdoor units. If connections are correct, isolate the power supply and then restore it to reset the system. If fault code E8 persists after this procedure, it is necessary to replace the indoor unit controller board or the outdoor unit controller board.
When should you call an F-Gas engineer?
Contact an F-Gas registered engineer if the fault returns after basic checks, involves refrigerant charging, or requires PCB or compressor replacement on Mitsubishi Electric.
Affected models
- Ecodan PUHZ HW140VHA2 BS
- Ecodan PUHZ HW140YHA2 BS
- Ecodan ATW PUHZ W50VHA BS
- Ecodan PUHZ SW50VKA BS
Field context
This code occurs during a critical loss of bidirectional communication between the indoor interface and the outdoor unit, preventing flow and temperature control. It specifically manifests when the outdoor unit remains silent for 3 minutes, indicating either a cable break or a defective controller board.
Frequently asked questions
What is the exact duration of no signal reception to trigger fault code E8?
Fault code E8 is triggered when the outdoor unit controller board receives no normal signal for a continuous period of 3 minutes. This condition indicates an interruption in communication with the indoor unit or a fault in the reception circuit on the outdoor board.
What is the first diagnostic step before replacing components?
Before any replacement, it is essential to check for disconnection or loose cables between the indoor and outdoor units. Then, perform a power cycle (isolate and restore power) to reset the system and check if the fault persists.
Which components should be replaced if fault code E8 persists after reset?
If fault code E8 reappears after checking connections and performing a power cycle reset, it is necessary to replace either the Interface/Flow temp. controller board of the indoor unit or the outdoor unit controller board, depending on the precise diagnosis of the faulty circuit.
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