What happens
A healthy valve receives the wrong operating request because sensing, setup or startup position is incorrect.
Typical symptoms
Poor feed appears after a board replacement or commissioning change without a proven valve-circuit defect.
Checks that distinguish this cause
Compare service-tool inputs, installed parts and required initialization with the specific model instructions. Establish whether commanded movement is reasonable for the actual load and mode.
What can look similar
A physically sticking valve can also fail after an apparently normal initialization.
Repair direction
Correct the verified input or configuration issue before replacing the valve.
Verify the repair
Verify repeatable initialization and appropriate feed during changing demand.
Equipment-specific limits
A commanded step count is not proof of actual valve position. Coil pinouts, drive signals, initialization and resistance limits depend on the installed assembly.
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.
- Senville: R-454B model documentationSeparate installation and service documents for indoor styles and multi-zone generations.
Editorial review: 2026-09-29. Verify the current manual for the installed model.