Sensi Smart Thermostats Error Codes

App Cannot Find Thermostat

Sensi app cannot discover or connect to the thermostat during setup

Pairing / Provisioning Failure

Blank Screen

Sensi thermostat screen is completely blank and unresponsive

Loss of 24 V Control Power

E1

Thermostat displays E1 and will not control heating or cooling

Indoor Temperature Sensor Fault

E2

Thermostat displays E2 and shows no or incorrect temperature reading

Outdoor Temperature Sensor / Remote Sensor Fault (models that support external sensor)

E3

Thermostat displays E3 and system will not run correctly in heat or cool

System Configuration / Equipment Type Error

E4

Thermostat displays E4 and will not complete Wi‑Fi setup

Wi‑Fi Radio or Network Configuration Error

E5

Thermostat displays E5 and screen may be dim or unresponsive

Low Voltage / Power Supply Error

E6

Thermostat displays E6 and cannot control the HVAC system

Communication Error with HVAC Control Circuit

E7

Thermostat displays E7 and will not operate in heat pump mode correctly

Reversing Valve / O-B Circuit Error

E8

Thermostat displays E8 and ignores temperature setpoint changes

Internal Calibration / Sensor Range Error

E9

Thermostat displays E9 and may reboot repeatedly

Internal Memory / Firmware Error

Flashing Cool Icon

Cool icon flashes but outdoor AC unit does not start

Call for Cooling Not Reaching Condenser

Flashing Heat Icon

Heat icon flashes but furnace does not start

Call for Heat Not Reaching Furnace

Schedule Not Running

Sensi thermostat ignores programmed schedule and holds a single temperature

Software Scheduling / Hold Mode Misconfiguration

Wi‑Fi Icon Flashing

Wi‑Fi icon on Sensi thermostat flashes continuously and app shows thermostat offline

Network Connectivity Loss

Symptom

Thermostat backlight flickers or display brightness changes unexpectedly

Display Power Regulation Issue

Symptom

Thermostat beeps or chimes unexpectedly (on models with audible alerts)

Alert or Notification Behavior

Symptom

Thermostat calls for cooling but room temperature never reaches setpoint

Ineffective Cooling Control or Misconfigured System Type

Symptom

Thermostat calls for heat but furnace short cycles (turns on and off frequently)

Short Cycling Due to Thermostat Placement or Settings

Symptom

Thermostat clicks but HVAC equipment does not start

Relay Operation Without Load Activation

Symptom

Thermostat display fogs or shows condensation inside the lens

Moisture Intrusion into Thermostat Housing

Symptom

Thermostat displays "Aux Heat" frequently on a heat pump system

Excessive Auxiliary Heat Usage

Symptom

Thermostat does not power up unless batteries are installed (on battery‑assist models)

Insufficient C Wire Power / Battery Assist Dependency

Symptom

Thermostat does not respond to touch or button presses intermittently

User Interface / Capacitive Touch Failure

Symptom

Thermostat fan setting on AUTO but blower runs continuously

Continuous Fan Operation Not Commanded by Thermostat

Symptom

Thermostat frequently disconnects from Wi‑Fi but then reconnects

Intermittent Wireless Connectivity

Symptom

Thermostat loses date/time or settings after power outage

Non‑Volatile Memory / Backup Power Issue

Symptom

Thermostat mounting plate is loose or thermostat tilts on the wall

Mechanical Mounting Instability

Symptom

Thermostat plastic housing feels unusually warm to the touch

Internal Component Overheating

Symptom

Thermostat randomly reboots or restarts during normal operation

Intermittent Power or Internal Reset Condition

Symptom

Thermostat shows "Cooling" but only the indoor blower runs, outdoor unit stays off

Outdoor Unit Not Energized by Thermostat Call

Symptom

Thermostat shows "Heat On" but heat pump runs in cooling mode (blowing cold air)

Reversing Valve Misconfiguration

Symptom

Thermostat shows "Heating" but only the blower runs, no warm air

Heat Call Without Burner or Heat Source Activation

Symptom

Thermostat shows much higher or lower room temperature than actual

Temperature Sensing / Calibration Error