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ErrorLib — Industrial Fault Code Library

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E37-4

Outdoor Heat Exchanger Thermistor 4 Failure (Tho-R4)

Mitsubishi Electric · R410A Systems

What does E37-4 mean?

The fourth outdoor heat exchanger thermistor (Tho-R4) is defective. This prevents accurate temperature measurement of a specific section of the outdoor coil, impacting system control and protection.

Common Causes

  • Outdoor heat exchanger thermistor 4 (Tho-R4) has failed.
  • Wiring to Tho-R4 is broken or shorted.
  • Tho-R4 reading is out of specified limits.
  • Defective Tho-R4 thermistor.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Measure the resistance of thermistor Tho-R4 at its leads — compare to a resistance-temperature chart if available.

  2. 2

    Inspect the connector for Tho-R4 on the outdoor unit PCB — verify it is securely seated and free from corrosion.

Browse all codes in this manual (60)
Verified technical data. Last updated: April 2026

Related Faults

E0Transmitting/Receiving Signal ErrorE112Auto Addressing Conflict / Factory Address Setting ErrorE14Master/Slave System Configuration Error
Source: Mitsubishi Electric R410A Systems
Open Manual (Page 4)Search more codes in this manual