What happens
The controller receives an input outside the sensor circuit’s valid electrical range.
Typical symptoms
Sensor-related fault, inhibited operation or a temperature reading that cannot represent the actual location.
Checks that distinguish this cause
Identify the named sensor in the exact fault definition. Isolate power, separate the sensor from electronics as directed and evaluate the sensor and harness independently against model data at a known temperature.
What can look similar
A board input failure can produce a sensor report even when the sensing element and harness are intact.
Repair direction
Repair the confirmed harness fault or replace the correctly specified sensing element; replace a board only after the input path is established.
Verify the repair
Compare displayed or service-tool temperatures with a suitable reference and confirm fault-free operation.
Equipment-specific limits
Use the exact sensor curve, connector pinout and temperature reference. There is no universal mini-split thermistor resistance, test voltage or interchangeable code table.
Practice this diagnosis
This cause is a reference topic; it does not yet have a dedicated simulated call. Browse the practice board.
References and applicability
Original HVACSim explanations with manufacturer and instrument-maker references for further reading. These resources support the subject; their model-specific examples are not specifications for every system.
- Daikin: 17 Series service manualModel-specific sensor and control examples; terminal values and code definitions vary.
- Haier: Arctic Next Gen service manualAW/1U EH2VHD model examples of inverter, motor, sensor and circuit diagnostics; obtain the installed model manual.
Editorial review: 2026-09-29. Verify the current manual for the installed model.