Sensi "Loss of Cooling" or "Loss of Heating" Alert?
- System called for heat/cool but the temperature did not respond
- Dirty filter or frozen coil limiting output
- Outdoor unit lost power (cooling)
Problem Description
You received a Loss of Cooling or Loss of Heating alert from the Sensi app. This alert means the thermostat called for cooling or heating but the room temperature did not change the way it expected, so it suspects the equipment is not delivering. It is a helpful early warning of an HVAC problem, and the fix is to find why the system is not keeping up.
Why This Happens in Real Homes
A Loss of Cooling or Loss of Heating alert from Sensi is one of the more useful things a smart thermostat does: it watches whether the room actually responds when it calls for heating or cooling, and when the temperature does not move as expected, it warns you that the equipment may not be delivering. It is not a thermostat malfunction, it is an early warning of an HVAC problem, and the investigation follows the equipment. Airflow comes first, since a dirty filter or a frozen coil is the most common reason output drops. For cooling, the classic cause is the outdoor unit losing power at the breaker or disconnect; for heating, the furnace control board's flash code points to ignition or safety faults. Extreme weather can trip the alert harmlessly when the system simply cannot reach an aggressive target. But a repeated alert with clean filters and powered equipment is a genuine prompt to have the system serviced, because it often catches a failing compressor, low refrigerant, or a furnace fault before it becomes a no-heat or no-cool emergency.
Symptoms
- Loss of Cooling alert in the Sensi app
- Loss of Heating alert in the app
- Room not reaching the setpoint
- Alert during a heat wave or cold snap
- System runs but the temperature does not move
- Repeated alerts over several days
- Alert after a filter or equipment issue
- Not sure what the alert means
Recognize these? Here's what usually causes it.
Common Causes
- System called for heat/cool but the temperature did not respond
- Dirty filter or frozen coil limiting output
- Outdoor unit lost power (cooling)
- Furnace lockout or ignition failure (heating)
- Low refrigerant reducing cooling capacity
- Extreme weather beyond system capacity
- Thermostat placement causing a false lag
- Equipment failure needing service
Most fixes happen in the first 3 steps.
If the alert coincides with no heat or no cooling in extreme weather, treat it as urgent. Refrigerant and combustion issues require a licensed HVAC professional.
Tools & Requirements
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Multimeter
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Step-by-Step Solution
Understand What the Alert Means
Sensi watches whether the room temperature responds to a heat or cool call. When it calls for cooling or heating and the temperature does not move as expected within a reasonable time, it sends a Loss of Cooling or Loss of Heating alert. It is not a thermostat fault; it is the thermostat flagging that the equipment does not seem to be delivering.
Check Airflow First
A dirty filter is the most common reason output drops. Replace it, and in cooling check the indoor coil for ice (a frozen coil stops cold air), thawing it with the system Off and fan On if needed. Restored airflow often clears the alert.
For Cooling, Check the Outdoor Unit
If it is a Loss of Cooling alert, confirm the outdoor condenser has power: check the AC breaker in the panel and the disconnect switch in the box beside the outdoor unit. A tripped breaker or pulled disconnect leaves the indoor fan blowing warm air, which triggers the alert.
For Heating, Read the Furnace
If it is a Loss of Heating alert, look at the furnace control board's blinking LED and match it to the code legend on the furnace door. Ignition lockouts, a bad flame sensor, or a pressure-switch fault stop heat and trip the alert. Also confirm the furnace power switch is on.
Consider the Weather
During extreme heat or cold, the system may simply be unable to reach an aggressive setpoint, which reads as a lack of response and triggers the alert even though nothing is broken. Set a realistic target during weather extremes.
Check Thermostat Placement
If the Sensi is somewhere that lags the real room (a cold exterior wall, a spot with poor air circulation), it may perceive slow response and alert. Confirm it is on a representative interior wall away from vents and drafts.
Look at Refrigerant and Capacity
If cooling runs but underperforms repeatedly, low refrigerant from a leak reduces capacity and keeps tripping the alert. That is an HVAC diagnosis. Persistent alerts with clean filters and powered equipment point to a real capacity or refrigerant problem.
Adjust or Acknowledge the Alert
Once you have addressed the cause, the alert clears when the system responds normally again. You can manage alert settings in the Sensi app, but treat repeated alerts as a genuine prompt to service the HVAC rather than something to simply silence.
Quick Solutions
Still having issues? This is usually the deeper cause below.
Notification delays almost always return after a major iOS or Android update — background app refresh gets reset to restricted on every major OS version.
Do not just dismiss a repeated Loss of Cooling or Heating alert; it is Sensi telling you the equipment is struggling. Catching a failing system early can prevent a total breakdown on the hottest or coldest day.
Notification delays over 2 minutes are almost never the device's fault — background app restrictions quietly re-enable themselves after every OS update.
- System called for heat/cool but the temperature did not
- Dirty filter or frozen coil limiting output
- Outdoor unit lost power (cooling)
- Furnace lockout or ignition failure (heating)
- Low refrigerant reducing cooling capacity
Before you go — try one of these (they fix most cases).
Most popular upgrades chosen by Emerson Sensi Thermostat owners.
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Official Manufacturer Manual
Emerson Sensi provides official product documentation through their online manual rather than downloadable PDF. Access setup guides, troubleshooting steps, and product specifications for your Emerson Sensi Thermostat.
Source: sensi.emerson.com
Need More Help? Emerson Sensi Support
Note: The contact information below connects you directly to Emerson Sensi's official customer support team, not Trunetto. They can help with warranty claims, device replacements, and advanced technical issues.
