e9
Moderate
Mitsubishi Electric · Mini-Splits & Ductless Systems
Serial Communication Error (Expansion Valve)
Quick Answer
Error code E9 on your Mitsubishi Electric Mini-Splits & Ductless Systems means: Serial Communication Error (Expansion Valve). This is usually fixable — see the step-by-step guide below.
Affected Models
Applies to all models
Likely Causes
How to Fix It
1
Power cycle the unit and monitor for code recurrence
2
Check the expansion valve connector and wiring at the indoor PCB
3
Verify the expansion valve driver board is receiving proper signals
4
Measure the expansion valve coil resistance (compare to manufacturer specifications)
5
This is a complex repair requiring a licensed HVAC technician with Mitsubishi mini-split experience
Pro Tip
This fix requires some technical knowledge. If you're unsure about any step, consider contacting support or a qualified technician.
Parts You May Need
Electronic expansion valve
Expansion valve driver board
Indoor PCB
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