Error code reference

Aprilaire HVAC Error Code E4

Insufficient Capacity: The suction line temperature has not dropped at least 5°F in 20 minutes from the temperature when the compressor started, indicating the compressor is not running or the refrigeration system is not operating properly.

SourceAprilaire Dehumidifier - Service Manual: Models 1830, 1850, 1870p. 4

Aprilaire codes Aprilaire hvac codes

Diagnostic procedure

The full E4 procedure

Step 1 is visible so you can confirm you are on the right page. The remaining steps, the ones that tell you whether to actually replace a part, unlock with any pass.

MyPros+ · DiagnosticsStep 1 preview

First diagnostic step

Use the ON/OFF button to turn the mode to OFF, flip the ON/OFF toggle switch OFF to reset the code, then enter Installer Test Mode to verify compressor operation.

SourceAprilaire Dehumidifier - Service Manual: Models 1830, 1850, 1870p. 4

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More steps, wiring diagram references, and verified part numbers

Includes expected resistance and voltage values, connector pinouts, and supersession notes for replacement parts.

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Where this code is documented

3 manuals in the MyPros+ library document this code for Aprilaire hvac.

Models covered by the manuals that document this code

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The full E4 procedure

Where this code is documented

Models covered by the manuals that document this code

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