Symptom
Aux heat running all the time?
Auxiliary heat is the backup — usually electric resistance — that helps a heat pump in very cold weather or during defrost. If the thermostat shows AUX most of the time in mild weather, or the winter bill jumps with no change in comfort, the heat pump may be underperforming or the controls may be set up to call backup heat too early.
Worth booking. Not dangerous, but expensive every day it continues. Book a visit.
What usually causes this.
These are the common possibilities, not a diagnosis. A page cannot tell which one it is — that takes a technician testing the system.
- Outdoor unit
- Thermostat
- Heat section
- Thermostat configuration
- Thermostats not set up for the specific heat pump, or with aggressive recovery settings, call backup heat more than needed.
- Large temperature setbacks
- Turning the heat down a lot overnight and back up in the morning can bring on backup heat to catch up.
- Heat pump losing capacity
- A low refrigerant charge, dirty coils or an airflow problem makes the heat pump fall behind, so backup heat covers the gap.
- Outdoor temperature sensor or lockout settings
- Where fitted, these decide when backup heat is allowed. Wrong settings let it run in mild weather.
- Defrost problems
- Backup heat usually runs during defrost. Excessive defrost means excessive backup heat.
What you can safely check.
- Check the thermostat is in Heat, not Emergency Heat.
- Try smaller temperature setbacks — a steady setting is often more efficient with a heat pump.
- Replace the filter and clear the outdoor unit.
- Compare this winter's bills with last year's for the same months to confirm the change.
Leave these alone
- Thermostat installer or wiring settings, unless you're confident with them.
- The indoor unit's electric heat strips and their wiring.
Call rather than book online if:
- You smell burning from the indoor unit when backup heat runs
What we check when we get there.
In order, and every time — the point of a diagnostic is to find out which cause it is before anything is replaced.
- 01The technician checks the heat pump's own performance — charge, airflow and defrost — then reviews thermostat configuration and backup-heat staging so backup heat runs only when it should.
What it is likely to cost.
Sometimes the fix is a configuration change during the diagnostic visit. If the heat pump itself is underperforming, the repair is priced before any work.
- Diagnostic
- $89
- Refrigerant leak / recharge
- From $499
- Smart thermostat installation
- From $299
Prices are starting points for standard work in the Savannah area. Final price depends on the system and site, and is confirmed before work begins. Permits and code-required upgrades may be additional.
Questions people ask about this.
- What's the difference between AUX and EM heat?
- AUX means the thermostat has automatically brought in backup heat to help the heat pump. EM (emergency) heat means you've switched the heat pump off and are running only on backup heat — useful if the heat pump fails, but expensive.
- Is it normal to see AUX heat sometimes?
- Yes — on the coldest mornings, during defrost, and when you raise the set point a lot. Seeing it most of the time in mild weather isn't.
Work out the decision:SEER2 Explained
Further reading:Heat pump or gas furnace on the Georgia coast?
The service that fixes it.
Heat Pump Service & Installation is the work behind this symptom. Its page covers what is involved, how it is quoted and what we stand behind.
Symptoms that sit next to it.
Systems rarely fail in one way only. If one of these is also true, say so when you book — it narrows the diagnosis before anyone arrives.
Furnace or heat pump not heating, blowing cold air, cycling or running up the bill.
- Furnace won't turn on or lightA gas furnace that won't light is most often a worn igniter, a dirty flame sensor, a clogged filter tripping a safety limit, or a thermostat or power problem.
- Furnace blowing cold airA furnace blowing cold air is often a thermostat set to fan On rather than Auto, a furnace that has shut its burners off on a safety limit, or an ignition problem.
- Furnace turning on and offA furnace that runs for a few minutes, shuts off and restarts over and over is short cycling.
- Heat pump not heatingA heat pump that runs but doesn't heat well may have a thermostat set incorrectly, a dirty filter, an iced-up outdoor coil, a low refrigerant charge, or a reversing valve or defrost problem.
- Heat pump iced up or stuck in defrostIn cold, damp weather a heat pump's outdoor coil collects frost, and the system runs a defrost cycle to melt it — steam and a few minutes of cooler indoor air are normal.
Not sure which it is?Describe it to the assistant
Everything else we are called about.
The whole index, in three groups.
HUMIDITY, AIRFLOW & ENERGY BILLS
House feels humid or dampSome rooms too hot or coldPower bill suddenly higher
Get it looked at.
We cover Savannah, the Coastal Empire and the South Carolina Lowcountry. Tell us what the system is doing — you do not need to know the cause. The diagnostic price is given to you before the visit, and the repair price before any work starts.
No heat, or no cooling at all?Call rather than send a request — (912) 858-3737 is answered around the clock.