What Does Ecobee 'Aux Heat Running' Mean and How Do I Stop It From Running Constantly?
- Heat pump outdoor unit not running due to defrost board failure or contactor issue
- Thermostat set point raised more than 3 degrees at once triggering aux heat
- Compressor lockout temperature set too high causing premature switch to aux
Problem Description
Your Ecobee thermostat shows Aux Heat Running or your electric bill has spiked dramatically because the auxiliary heat strips in your heat pump system are running excessively. Auxiliary heat is the electric resistance backup heater built into your heat pump air handler. It is designed to supplement the heat pump only during extreme cold when the heat pump alone cannot keep up. However if aux heat runs frequently or constantly it means something is wrong because electric resistance heat costs 2 to 3 times more than heat pump heating. Excessive aux heat is one of the most expensive HVAC problems homeowners face.
Symptoms
- Ecobee shows Aux Heat Running frequently or constantly
- Electric bill increased dramatically during heating season
- Heat pump outdoor unit fan not spinning when system is heating
- Home takes a very long time to reach set temperature
- Aux heat kicks on even when outdoor temperature is above 40 degrees
- System blows very hot air instead of the normal warm air from heat pump
Recognize these? Here's what usually causes it.
Common Causes
- Heat pump outdoor unit not running due to defrost board failure or contactor issue
- Thermostat set point raised more than 3 degrees at once triggering aux heat
- Compressor lockout temperature set too high causing premature switch to aux
- Low refrigerant reducing heat pump capacity forcing aux to compensate
- Outdoor unit coils frozen preventing heat pump operation
- Ecobee aux heat threshold configured too aggressively
Most fixes happen in the first 3 steps.
Do not disable aux heat entirely by disconnecting the W2 wire. In extreme cold the heat pump alone cannot keep your home warm and pipes could freeze. Aux heat is a necessary safety backup. The goal is to minimize unnecessary aux heat usage not eliminate it completely.
Step-by-Step Solution
Review aux heat lockout and thresholds
Check ecobee compressor lockout temperature and aux heat staging thresholds. Misconfigured lockouts can force auxiliary heat to run longer than expected.
Verify wiring at thermostat and air handler
Inspect W1/W2 and common wiring for correct terminal placement and secure connection. Crossed or loose heat-stage wiring can call auxiliary heat continuously.
Check outdoor sensor and weather inputs
Confirm external temperature readings are accurate and not stuck at low values. Incorrect outdoor data can trigger unnecessary aux heat operation.
Disable temporary holds and review schedule
Remove manual holds and inspect schedule transitions that may maintain high setpoints. Extended setpoint gaps often keep aux heat active during recovery.
Run equipment test and monitor stage calls
Use ecobee equipment test to verify stage transitions and runtime behavior. If aux heat remains active incorrectly, escalate for HVAC control board diagnostics.
Quick Solutions
Still having issues? This is usually the deeper cause below.
If this comes back after following these steps, check whether a recent app or firmware update reset a default setting — the fix works, but the setting gets reverted silently.
The Ecobee Home IQ report shows exactly how many hours aux heat ran each day compared to heat pump heating. Check this weekly during winter. If aux heat hours are consistently more than 10 percent of total heating hours something needs attention. Ideally aux heat should only run a few hours per month in moderate climates.
This issue almost always looks more complex than it is — the majority of cases trace back to a single setting, a stale credential, or a default that shipped wrong.
- Heat pump outdoor unit not running
- Thermostat set point raised more than 3 degrees at
- Compressor lockout temperature set too high
- Low refrigerant reducing heat pump capacity forcing aux to
- Outdoor unit coils frozen preventing heat pump operation
Before you go — try one of these (they fix most cases).
Most popular upgrades chosen by Ecobee Smart Thermostat owners.
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Official Manufacturer Manual
Ecobee provides official product documentation through their online manual rather than downloadable PDF. Access setup guides, troubleshooting steps, and product specifications for your Ecobee Smart Thermostat.
Source: ecobee.com
Need More Help? Ecobee Support
Note: The contact information below connects you directly to Ecobee's official customer support team, not Trunetto. They can help with warranty claims, device replacements, and advanced technical issues.
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