Heat pumps have failure modes an ordinary furnace does not — and one very common false alarm that is not a fault at all.
Know where to stop
Everything below is a check any homeowner can safely make. Anything involving opening a sealed refrigerant circuit, working inside an energized panel, or dismantling a gas train needs a licensed technician — not because we want the call, but because that is where people get hurt.
If you smell gas, leave the building and call the gas utility from outside.
Free things to try before you call
A good share of the calls we go out on turn out to be one of these. Try them first, and you may save yourself a service charge.
- 01
Check the thermostat is on HEAT, not on EMERGENCY HEAT, and the setpoint is above room temperature
- 02
Replace the air filter and open all supply registers
- 03
Check breakers for both the indoor air handler and the outdoor unit
- 04
Look at the outdoor unit — if it is encased in solid ice, the defrost cycle is not working
- 05
Clear snow, ice and leaves from around and on top of the outdoor unit
- 06
Make sure the outdoor unit is not sitting in a puddle or blocked by drifted snow
- 07
Feel the supply air — heat pump air is cooler than furnace air and can feel wrong while working
- 08
Check whether auxiliary heat is running constantly, which points at a heat pump not keeping up
What it probably is
These are the most likely causes. Open one to see what it looks like and what fixing it involves.
1Normal operation mistaken for a fault
It is worth saying first: heat pump supply air runs cooler than furnace air — often around body temperature — so it can feel cool against your hand while heating the house perfectly well. If the house is holding temperature, nothing is wrong.
2A failed defrost cycle
The outdoor coil ices in cold damp weather, and the unit periodically reverses to melt it off. When the defrost board or sensor fails, ice builds until the unit is solid and cannot exchange heat at all. A unit encased in ice is the signature symptom.
3A stuck reversing valve
The reversing valve is what makes a heat pump able to run backwards. When it sticks, the unit is stuck in cooling mode — so it blows cold air in winter. It is distinctive and easy to recognize.
4Auxiliary heat running constantly
If the heat pump is not producing, the backup electric strips carry the whole load. The house stays warm and the electricity bill can triple. No alarm goes off, which is why people often discover it on a bill rather than at the thermostat.
5Low refrigerant charge
A heat pump low on refrigerant loses heating capacity before it loses cooling capacity, so winter is often when a small summer leak first announces itself.
Common follow-ups
Why is my heat pump steaming outside?
That is a normal defrost cycle — the unit briefly reverses to melt ice off the outdoor coil, and the steam is that ice evaporating. It should last a few minutes and then return to heating.
Should I use emergency heat?
Only if the heat pump has failed. Emergency heat locks the heat pump out and runs the expensive backup alone. It is a way to stay warm until we arrive, not a setting to leave on.
Should I pour hot water on the ice?
Warm — not hot — water will clear ice in an emergency, and never use anything sharp to chip at it; the coil fins puncture easily and that turns a repair into a replacement. If it keeps icing, the defrost system needs attention.
Prefer to call?
(423) 357-1922- Office hours
- Monday to Friday, 8–5
- Outside those hours
- Emergency service is available — call the same number.
- Where we go
- Church Hill, Kingsport, Mount Carmel, Surgoinsville, Rogersville, Johnson City, Bristol, Greeneville, Morristown and across into Southwest Virginia. Full service area.
- Where we are
- 119 E Main St, Church Hill, TN 37642
Still not working after these checks?
That is what we are here for, and emergency service is available.
(423) 357-1922