Troubleshooting guide
Heat pump iced over outside? Here is what is happening and what to do.
A heat pump iced over outside is normal during cold weather defrost cycles. It becomes a problem if the ice doesn't clear within 30-45 minutes, or if the unit is fully encased. Causes of persistent icing include defrost sensor failure, low refrigerant, restricted airflow, or buried/blocked outdoor unit. Clear snow and debris first. Then call.
Likely causes, ranked by probability
- 1
Blocked outdoor airflow
Snow, leaves, or shrubs preventing defrost.
Likelihood 30%
- 2
Failed defrost sensor
Sensor doesn't trigger defrost cycle.
Likelihood 30%
- 3
Low refrigerant
Reduces capacity and increases ice buildup.
Likelihood 25%
- 4
Defrost board failure
Board doesn't initiate defrost cycle.
Likelihood 15%
What you can try first
- · Clear snow and debris from around the outdoor unit
- · Turn the system off and let ice melt naturally
When to call us: Ice returns within 4 hours of clearing the area.
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 iced over outside dangerous?
Most causes of "heat pump iced over outside" are not immediately dangerous, but ignoring them can damage the system over time. Ice returns within 4 hours of clearing the area.
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.