Troubleshooting guide
Heat pump not heating? Here is what is happening and what to do.
A heat pump that won't heat is most often caused by a frozen outdoor coil, a tripped breaker, a dirty filter restricting airflow, a refrigerant issue, or a stuck reversing valve. The first three you can check yourself. The last two require a tech. Don't run the system for long periods if it's not heating, you can damage the compressor.
Likely causes, ranked by probability
- 1
Frozen outdoor coil
Persistent icing prevents heat exchange. Often points to a defrost sensor or refrigerant issue.
Likelihood 30%
- 2
Tripped breaker or disconnect
No power reaching the outdoor unit. Check the panel and the disconnect box outside.
Likelihood 20%
- 3
Dirty filter restricting airflow
Forces the system into protection mode and reduces heat output.
Likelihood 20%
- 4
Low refrigerant
Slow leak reducing capacity. Requires diagnosis and recharge by a tech.
Likelihood 15%
- 5
Stuck reversing valve
The valve that switches between heat and cool modes is jammed. Requires service.
Likelihood 15%
What you can try first
- · Check the breaker and outdoor disconnect
- · Wash or replace the indoor filter
- · Clear snow and ice from around the outdoor unit
When to call us: Outdoor coil stays iced over for more than 45 minutes after defrost cycle, or the system blows cold air for more than an hour.
When a cleaning helps, and when to call a repair pro
A good portion of “something is off” symptoms (musty smell, weak airflow, water dripping from the indoor unit, surface mold) trace back to a dirty blower wheel, clogged drain, or biofilm on the coil. A full disassembly cleaning solves those. If we get on site and find an electrical or mechanical fault (a failing capacitor, a stuck reversing valve, refrigerant issues), we will tell you and recommend a heat pump repair contractor. We do not do repairs ourselves.
Frequently asked questions
Is heat pump not heating dangerous?
Most causes of "heat pump not heating" are not immediately dangerous, but ignoring them can damage the system over time. Outdoor coil stays iced over for more than 45 minutes after defrost cycle, or the system blows cold air for more than an hour.
Can a cleaning fix this?
Sometimes. Biofilm, dirty coils, and clogged drain lines often resolve after a deep clean. Mechanical or electrical issues need a heat pump repair contractor instead.
Do you do repairs?
No. We focus on cleaning and twice-yearly maintenance. If your system needs a part replaced or an electrical fix, we will tell you what we see and recommend a repair contractor.
Try a cleaning first.
If the symptom traces back to a dirty unit, we can fix it. If it does not, we will tell you and point you to a repair pro.