Mitsubishi Electric U4

Medium

Mr. Slim — Outdoor thermistor fault (open/short).

Mitsubishi Electric U4: Outdoor thermistor fault (open/short). This fault usually isn't an immediate stop, but should be checked soon.

Possible causes

Thermistor faulty.
Connector loose.

Check steps

Check thermistor connector.
Measure thermistor resistance: 10kΩ@25°C.
Replace thermistor.

Affected parts

Außenthermistor

Safety note

230V — isolate power.

Source: Mitsubishi Electric resmi servis kılavuzu — Same official reference, 'Output pattern B' table: 'U3, U4 — Open/short of outdoor unit thermistors'. PUY-P/PUY-M table further specifies: 'U3/U4 — Open/short of discharge thermistor (TH4) and comp. surface thermistor (TH32/33) / Open/short of outdoor thermistors (TH3, TH6, TH7,…

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

Look up in Enthalio →

Related fault codes

Indoor/outdoor communication error.E6 High discharge temperature — compressor overheU2 Pipe temperature error (often defrost/thermistP8 Intake (room) thermistor fault.P1 Pipe (liquid) thermistor fault.P2 Drain float switch / drain sensor fault.P4