What Does Nest Thermostat Error E298 Mean and How Do I Fix Cooling Running Too Long?
- Low refrigerant in the AC system due to a leak
- Dirty or clogged outdoor condenser coils reducing cooling capacity
- Clogged air filter restricting airflow through the system
Problem Description
Your Nest thermostat is displaying error code E298 which means the thermostat has detected that your cooling system has been running for an abnormally long time without reaching the set temperature. The Nest monitors how long the AC runs and if it exceeds the expected duration for your home it flags E298 as a warning. This error indicates your cooling system is struggling and may have a problem such as low refrigerant, a dirty condenser, a failing compressor, or the thermostat set point being unrealistically low for extreme heat conditions. Your AC continues running but is not cooling your home effectively.
Symptoms
- Nest thermostat shows E298 error code
- AC runs continuously for hours without reaching set temperature
- Home temperature stays 5 to 10 degrees above the thermostat setting
- Electric bill significantly higher than usual
- AC blows air but it is not as cold as it should be
- Error appears during hot summer days when outside temperature exceeds 95 degrees
Recognize these? Here's what usually causes it.
Common Causes
- Low refrigerant in the AC system due to a leak
- Dirty or clogged outdoor condenser coils reducing cooling capacity
- Clogged air filter restricting airflow through the system
- AC unit undersized for the home square footage
- Extreme outdoor temperatures exceeding system design capacity
- Failing compressor not pumping refrigerant efficiently
Most fixes happen in the first 3 steps.
E298 can indicate a refrigerant leak. Refrigerant is a regulated substance and only a licensed HVAC technician should handle it. Do not attempt to recharge refrigerant yourself. Low refrigerant also causes the evaporator coil to freeze over. If you see ice on the copper lines or the indoor coil turn off the AC and run only the fan to defrost before calling for service.
Tools & Requirements
These tools will help you complete this fix.
Garden hose for condenser cleaning
WiFi Sprinkler Timer, Smart Bluetooth Hose Timers, W...
Replacement air filter
Levoit Vital 100 Air Purifier Genuine Replacement Fi...
As an Amazon Associate we earn from qualifying purchases.
Step-by-Step Solution
Replace the Air Filter
A dirty air filter is the easiest and most common fix for E298. A clogged filter restricts airflow forcing the AC to run longer to cool your home. Locate your air filter in the return air vent or inside the air handler. If the filter is visibly dirty or has not been changed in over 3 months replace it with a new filter of the same size. After replacement the AC should cool more efficiently and reach the set temperature faster.
Needed for this step
Levoit Vital 100 Air Purifier Genuine Replaceme...
$54.99Clean the Outdoor Condenser
Go to your outdoor AC unit. Check if the metal fins on the outside are clogged with dirt, grass, leaves, or cottonwood seeds. Dirty condenser coils cannot release heat effectively reducing cooling capacity. Turn off the AC at the thermostat. Use a garden hose with a gentle spray to clean the coils from the inside out. Remove any debris around the unit and ensure at least 2 feet of clearance on all sides for airflow. Turn the AC back on after cleaning.
Needed for this step
WiFi Sprinkler Timer, Smart Bluetooth Hose Time...
$39.99Check Vents and Registers
Walk through every room and verify all supply vents and return air grilles are fully open and not blocked by furniture, rugs, or curtains. Closed or blocked vents restrict airflow forcing the AC to run longer. Even one or two blocked vents in a large room can significantly impact cooling performance. Open all vents regardless of whether the room is in use.
Raise the Set Temperature During Extreme Heat
Most residential AC systems are designed to cool 20 degrees below the outdoor temperature. If it is 105 degrees outside and your thermostat is set to 72 the system physically cannot maintain that temperature and will run continuously triggering E298. During extreme heat raise the set point to 76 to 78 degrees. The AC will cycle normally and E298 should clear within a few hours.
Schedule Professional HVAC Service
If replacing the filter, cleaning the condenser, and opening vents do not resolve E298 the AC likely has a mechanical issue requiring professional service. Low refrigerant from a leak is the most common cause of poor cooling that the homeowner cannot fix. Call a licensed HVAC technician to check refrigerant charge, compressor health, and ductwork integrity. Mention the E298 error code so they can target their diagnosis.
Quick Solutions
Still having issues? This is usually the deeper cause below.
Schedules that skip randomly are usually a daylight-saving holdover — delete and recreate the schedule to clear the corrupted entry.
The Nest thermostat learns your home cooling patterns over time. After fixing the root cause of E298 it may take 1 to 2 days for the thermostat to recalibrate and stop showing the warning. If the AC is now cooling normally the error will clear on its own. **Product Intelligence:** - C-wire required for most models - 2.4GHz WiFi only - Nest Aware subscription for history
Thermostat issues that keep returning are often caused by stale backup-battery memory holding old settings across power cycles without the user realising.
- Low refrigerant in the AC system
- Dirty or clogged outdoor condenser coils reducing cooling capacity
- Clogged air filter restricting airflow through the system
- AC unit undersized for the home square footage
- Extreme outdoor temperatures exceeding system design capacity
Before you go — try one of these (they fix most cases).
Most popular upgrades chosen by Google Nest Thermostat owners.
Google Nest Thermostat Trim Kit - Made for the Nest Therm...
Google Nest Thermostat Trim Kit - Made for the Nest Therm...
Google Nest Thermostat - Smart Thermostat for Home - Prog...
As an Amazon Associate we earn from qualifying purchases.
Official Manufacturer Manual
Google Nest provides official product documentation through their online manual rather than downloadable PDF. Access setup guides, troubleshooting steps, and product specifications for your Google Nest Thermostat.
Source: google.com
Need More Help? Google Nest Support
Note: The contact information below connects you directly to Google Nest's official customer support team, not Trunetto. They can help with warranty claims, device replacements, and advanced technical issues.
How Does Google Nest Compare?
Before replacing your Google Nest device, see how it stacks up against alternatives in our full comparison guides.
