Johnson Controls
Ineffective Dehumidification Control
Thermostat and HVAC system run, but indoor humidity remains high and does not reach the setpoint.
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Dehumidification feature disabled, Incorrect humidity setpoint, Miswired dehumidifier or DH terminal, Oversized AC system short cycling
How to Fix / Troubleshooting
Safety: Turn off power before modifying any dehumidifier wiring.
- Step 1 – Verify humidity settings: Ensure the dehumidification feature is enabled and the humidity setpoint is reasonable (e.g., 45–50%).
- Step 2 – Check wiring: Confirm the dehumidifier or DH terminal is wired according to Johnson Controls and equipment manuals.
- Step 3 – Confirm device operation: Manually force a dehumidification call from the thermostat and listen for the dehumidifier or over‑cooling operation. If nothing happens, the control circuit may be miswired or the device failed.
- Step 4 – Runtime and sizing: If the AC is oversized and short cycles, it may not dehumidify effectively. Discuss equipment sizing and run‑time strategies with an HVAC professional.
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Repair Difficulty
Medium
3/5
Required Part
Dehumidifier Control Circuit / DH Output
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