Honeywell Thermostat Error Code Aux Heat: How to Fix It

Q: Is it expensive to run auxiliary heat on my Honeywell thermostat?

Yes, auxiliary heat typically costs 2-3 times more to operate than your heat pump because it uses electric resistance heating. However, it's designed to run temporarily during cold weather or when extra heating is needed.

Q: Should I turn off auxiliary heat manually?

No, don't disable auxiliary heat unless instructed by a technician. It's a backup system that prevents your home from getting too cold when the heat pump can't keep up. Disabling it could leave you without adequate heating during cold weather.

Q: Why does my Honeywell thermostat show Aux Heat when it's not that cold outside?

If auxiliary heat activates when outdoor temperatures are above 40°F, it usually indicates a problem with the heat pump system, such as low refrigerant, a faulty reversing valve, or compressor issues that require professional repair.

Q: How long should auxiliary heat run?

During cold weather below 35°F, auxiliary heat may run for extended periods. However, if outdoor temperatures are moderate and aux heat runs constantly for more than an hour, there's likely a heat pump problem that needs professional attention.

Q: What's the difference between Aux Heat and Em Heat on Honeywell thermostats?

Aux Heat activates automatically when extra heating is needed, while Em Heat (Emergency Heat) is manually activated and completely bypasses the heat pump. Em Heat should only be used when the heat pump is completely broken.

Abstract

When your Honeywell thermostat displays 'Aux Heat' or 'Em Heat', it means your backup heating system has activated because your primary heat pump isn't meeting the heating demand. This typically happens during extremely cold weather or when the heat pump system needs attention.