Reversing Valve Decision Logic
Test O/B control, coil energization, and pressure response to separate control signal issues from mechanical valve sticking.
System Diagnostics
Heat Pump Diagnostics Across Cooling and Heating Modes
ACLogics helps technicians resolve mode-change and defrost problems that look random but follow clear electrical and thermodynamic patterns.
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> CONFIDENCE: 98.4%
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> CONFIDENCE: 98.4%
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Built for Precision
Everything you need to diagnose with confidence and accuracy.
Defrost Control Validation
Evaluate sensor readings, board logic, and coil conditions so frost faults are solved without unnecessary board swaps.
Auxiliary Heat Sequencing
Confirm staging, lockout thresholds, and thermostat behavior when backup heat short cycles or fails to assist.
The Three-Step Workflow
01
Capture Seasonal Context
Enter ambient conditions, demand mode, and observed switching behavior at the thermostat and outdoor board.
02
Test by Failure Branch
Run mode-specific checks to isolate thermostat setup, control wiring, valve operation, or sensor feedback faults.
03
Finalize With Performance Proof
Confirm corrected operation in both modes and document your readings for service records.
Frequently Asked Questions
Unit is stuck in cooling while thermostat calls for heat. Is the reversing valve failed?
Not necessarily. Confirm thermostat O/B configuration and control voltage first. Misconfigured logic often mimics valve failure.
Outdoor coil frosts heavily but never enters defrost. Where should diagnosis start?
Start with coil sensor resistance and board input status, then verify timer logic and relay output. Sensor drift is a common hidden cause.
Auxiliary heat runs too often even in mild weather. Is the heat pump undercharged?
Charge can contribute, but staging and lockout settings are usually first. Verify thermostat balance-point logic and sensor calibration.
Suction pressure looks weak only in heating mode, not cooling mode. What does that indicate?
Focus on outdoor airflow, defrost residue, and heating-mode metering behavior. A heating-only airflow restriction is a common root cause.
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