Mitsubishi Electric U1

Critical

PUY-P42, 48, 125VKA.TH / PUY-M125VKA-SG — Abnormal high pressure (high pressure switch 63H/TRS operated)

Mitsubishi Electric U1: Abnormal high pressure (high pressure switch 63H/TRS operated) This fault typically halts operation and needs immediate attention.

Possible causes

Indoor/outdoor units have a short cycle on their air ducts
Heat exchanger or filter is dirty

Check steps

Check that connector (63H/TRS) on outdoor controller board is not disconnected
Measure resistance values on the linear expansion valve using a tester

Affected parts

63H/TRS pressure switch
Heat exchanger
Air filter
Linear expansion valve

Safety note

High-pressure side is under pressure — release pressure and disconnect power before servicing.

Source: Mitsubishi Electric resmi servis kilavuzu (bagimsiz cift-dogrulandi) — Mitsubishi Electric Mr. SLIM Outdoor Unit (PUY-P42, 48, 125VKA.TH / PUY-M125VKA-SG) self-diagnosis/malfunction table, document dated 20241024, "Outdoor Unit" indication table, entry No.9, Check code U1 (LED1 3-time blinking / LED2 2-time blinking): "Abnormal high pressure (High pressure switch 63H/TRS operated.)" —…

Reviewed by Anıl Güzeldemir — in the refrigeration machine room since 2006, developer of Enthalio.

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Related fault codes

Abnormality of voltage (overvoltage or undervoU9 Connector (63H/TRS) is open/disconnectedF5 Check code is not defined (typically wrong remEF Indoor/outdoor communication error.E6 High discharge temperature — compressor overheU2 Outdoor thermistor fault (open/short).U4