Error code reference

Aprilaire HVAC Error Code E9

Outdoor Temperature Sensor Failure: The signal from the Outdoor Temperature Sensor is out of range; shows only if the ventilation feature has been enabled and temperature limits selected.

SourceAprilaire Dehumidifier - Service Manual: Models 1830, 1850, 1870p. 9

Aprilaire codes Aprilaire hvac codes

Diagnostic procedure

The full E9 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

Remove the wiring access cover of the User Interface Assembly, remove the ODT Sensor terminal and measure resistance across the terminals to verify it is in range for the outdoor temperature. Replace sensor (8052) if shorted or open.

SourceAprilaire Dehumidifier - Service Manual: Models 1830, 1850, 1870p. 9

Unlock with pass

More steps, wiring diagram references, and verified part numbers

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

Unlock E9 procedure $9.95

Or subscribe: $29/month for all codes plus Max diagnostics, with 70 Max messages a day. Plus applicable tax.

Where this code is documented

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

Models covered by the manuals that document this code

75,000+ service documents · 20,000+ error codes · 100+ brands

Get Started

$29/month · Cancel anytime · Or $9.95 3-day pass · Plus applicable tax

The full E9 procedure

Where this code is documented

Models covered by the manuals that document this code

Related Aprilaire hvac error codes