Why is my heat pump not heating?
A heat pump that isn't heating is often doing something normal — in defrost mode it blows cool air for a few minutes, and heat pump air feels cooler than furnace air even when it's working correctly. Genuine faults are usually a frozen outdoor unit, low refrigerant, or backup heat that failed to engage when temperatures dropped.
Need someone now?
24/7 emergency service · Fredericton and southern New Brunswick
What you can safely check
- Is it actually defrosting?
- Steam off the outdoor unit and a few minutes of cool air every hour or so in cold weather is normal. Give it fifteen minutes before deciding something is wrong.
- Clear the outdoor unit
- Snow drifted against it, ice at the base, or leaves in the coil all choke it. Clear snow by hand or with a broom — never chip ice off the coil.
- Thermostat mode
- Confirm HEAT, not AUTO or EM HEAT. Left on emergency heat, you're running expensive backup heat and the pump itself never starts.
- Indoor filter
- Restricted airflow across the indoor coil cuts heat output before anything else fails.
What’s probably going on
- Iced-up outdoor coil
- A failed defrost cycle lets ice build until the unit can't absorb heat. Encased in ice means a failed defrost board, sensor or reversing valve — not a cold snap.
- Low refrigerant
- Heat pumps move heat rather than make it, so a leak shows up as weak heat long before it stops entirely. Refrigerant is licensed work.
- Backup heat not engaging
- Below its balance point the system needs supplementary heat. A failed element or relay means the house slowly loses ground on the coldest nights.
- Reversing valve stuck
- The valve that switches heating and cooling can stick — the unit runs but in the wrong mode.
Stop here and call
If the outdoor unit is a solid block of ice, or the house is losing temperature overnight in a cold snap, call. Below −20 a failing heat pump becomes a pipe-freezing problem fast.
What we do about it
We check refrigerant charge, test the defrost cycle and reversing valve, and confirm your backup heat actually engages at the temperature it should.
Still stuck?
Tell us what the system is doing and we’ll tell you what it takes to fix — free quotes, no obligation, and a straight answer about whether it’s worth repairing.