South Carolina Cold Catches Heat Pumps Off Guard
A heat pump that sailed through three mild winters can suddenly struggle the moment temperatures in Aiken dip into the upper 20s. That’s not a coincidence — it’s physics. Heat pumps extract warmth from outdoor air, and when that air gets genuinely cold, the system has to work significantly harder. Problems that were lurking beneath the surface all summer get exposed fast.
The good news is that most winter heat pump problems fall into a predictable set of categories. Knowing what to look for — and what’s actually normal — can save you from an unnecessary service call or, just as importantly, from ignoring something that’s quietly making the problem worse.
Problem 1: Ice Buildup on the Outdoor Unit
A light frost on the top and sides of your outdoor unit on a cold morning is completely normal. Heat pumps pull moisture from the air as they operate, and in cold weather, that moisture freezes. Your system is designed to handle this with a built-in defrost cycle that periodically melts the ice away.
The problem happens when ice accumulates heavily — covering the entire coil, building up on top of the unit, or refusing to clear even after the system has been running for hours. That level of ice restricts airflow so severely that your heat pump stops moving heat efficiently. Left long enough, it can damage the compressor, which is the single most expensive component in the system.
If you see thick ice that doesn’t thaw within an hour or two of normal operation, that’s a flag. Don’t try to chip the ice off manually — you can puncture the refrigerant lines. Call for a proper diagnosis instead.
Problem 2: A Defrost Cycle That Stops Working
The defrost cycle is one of those features most homeowners don’t know exists until it fails. Every 30 to 90 minutes (depending on conditions), your heat pump briefly switches into a mode that reverses refrigerant flow and melts frost off the outdoor coil. During this time, your outdoor unit may steam, your indoor air may feel slightly cooler, and the system may sound different. All of that is expected.
A defrost cycle failure is a different story. When the sensors, control board, or reversing valve malfunction, the system skips defrost entirely — and ice accumulates unchecked. From our experience serving the Central Savannah River Area for nearly 100 years, defrost control board failures and faulty outdoor temperature sensors are among the most common heat pump problems winter brings to our service calls in the Aiken and North Augusta area.
Signs of a failed defrost cycle include persistent heavy icing, your system running constantly without adequately heating the home, and noticeably higher energy bills — often an increase of $60 to $100 per month depending on the size of your home and how long the issue has been present.
Problem 3: The System Blows Cool Air Instead of Heat
This one generates a lot of confused calls. A heat pump in heating mode will sometimes deliver air that feels cool compared to a gas furnace — that’s normal, since heat pumps typically produce air in the 90–100°F range rather than the 120–140°F range of a gas system. But air that genuinely feels cold coming from the vents is a different matter.
The most common culprits are a stuck or failed reversing valve, low refrigerant, or a malfunctioning thermostat. The reversing valve is the component that lets your heat pump switch between heating and cooling modes — when it gets stuck in cooling mode, you get cold air in January. Refrigerant leaks reduce the system’s ability to transfer heat, which means you’re running the system hard and getting very little in return.
One thing worth knowing: if your system has backup electric resistance heat strips installed (common in this region), they may be compensating for a struggling compressor — masking the problem while your energy bill climbs quietly. This is a scenario our NATE-certified technicians see repeatedly during winter service calls.
Problem 4: Inadequate Heating When Temperatures Drop Below 35°F
Standard heat pumps have a performance threshold. As outdoor temperatures fall below 35–40°F, a heat pump’s efficiency drops considerably because there’s simply less heat energy available in the cold air to extract. This is a design characteristic, not necessarily a malfunction.
That said, there’s a difference between a heat pump that’s working hard to keep up and one that’s failing to maintain your set temperature even under conditions it should be able to handle. If your home in Aiken is set to 68°F and the system can’t get past 62°F on a 38°F day, something beyond the cold weather is likely wrong — a refrigerant shortage, failing compressor, or undersized system are the usual suspects.
The fix may be a targeted repair, or it may mean your system would benefit from an upgrade to a cold-climate heat pump rated for efficient operation down to 0°F. Modern Lennox cold-climate systems, for example, maintain strong performance at temperatures that would have rendered older equipment nearly useless. If you’ve been living with a heat pump installation that’s 12 or more years old, this winter might be the moment to seriously evaluate whether heating repair is enough or whether replacement makes more financial sense.
Problem 5: The Heat Pump Runs Constantly Without Reaching Temperature
A heat pump that never shuts off is one of the clearest signs something has gone wrong. On extremely cold days, longer run cycles are expected — the system is working harder to compensate for heat loss through your walls, windows, and roof. But continuous operation that never achieves the thermostat setpoint, day after day, points to a system that’s been compromised.
The underlying causes range from dirty or clogged air filters (which restrict airflow so severely that the system can’t transfer heat effectively) to refrigerant leaks, failing compressors, or ductwork issues that are losing conditioned air before it reaches your living space. Duct leakage is frequently overlooked — in older homes throughout the CSRA, we’ve found duct systems losing anywhere from 20 to 40 percent of heated air into unconditioned attic or crawlspace before it ever reaches a register.
A continuously running system is also an expensive one. Depending on your utility rates and home size, a heat pump running around the clock can add $150 to $250 to a single month’s electric bill compared to a properly functioning system. Catching the cause early is almost always cheaper than letting it run.
What’s Normal vs. What Needs a Professional
A few heat pump behaviors genuinely alarm homeowners but require no intervention. Outdoor steam during defrost, a brief pause before the fan restarts, auxiliary heat kicking on during very cold snaps — these are all designed behaviors. The system is doing its job.
Reach for the phone when you observe any of the following:
- Ice covering more than the top surface of the outdoor unit, or ice that hasn’t cleared after two hours of normal operation.
- Air from your vents that feels genuinely cold (not just cooler than a furnace) while the thermostat is set to heat.
- The system running continuously for more than 24 hours without reaching your set temperature under normal winter conditions.
- A sudden unexplained spike in your electric bill of $75 or more with no change in usage habits.
These aren’t problems that tend to resolve on their own. And in most cases, the longer they run, the more expensive the eventual repair becomes.
Why Local Experience Matters in This Climate
The Central Savannah River Area has a climate that doesn’t fit neatly into the categories that national HVAC guides assume. Winters here bring stretches of genuine cold interrupted by mild days, combined with the high humidity that defines this part of South Carolina and Georgia. That humidity accelerates coil icing, stresses defrost components, and creates conditions where a system that technically passes a standard inspection can still struggle through a cold week in Aiken.
Sig Cox has been diagnosing and repairing heat pump problems in this specific climate since 1926. That’s not background noise — it means our technicians have worked through enough local winters to know what fails here, why it fails, and what the right fix looks like for a home in this region rather than a home in Atlanta or Charlotte. Our team holds NATE certification, and we operate as a Lennox Premier Dealer, which gives us access to equipment and technical resources that aren’t available through every HVAC contractor.
For professional Heat Pump Repair backed by genuine regional expertise, it matters who you call — especially in the middle of a cold snap when you need answers fast and accurate, not guesswork.
One More Thing Most Homeowners Overlook
Scheduling a heating repair after something breaks is understandable, but the call we wish more homeowners would make is the one before the cold arrives. A pre-season inspection — checking refrigerant charge, testing the defrost cycle, inspecting electrical connections, and verifying airflow — typically runs $80 to $150 and can catch the conditions that become $800 to $1,500 emergency repairs in December or January.
If you’re searching for heating repair near me or wondering whether your system is ready for another winter, an honest evaluation from a qualified technician is the fastest way to get clarity. If a repair is the right answer, you’ll know exactly what and why. If the system is in good shape, you’ll have that confirmed and can stop wondering.
Either way, you’re better positioned than if you wait until the first hard freeze to find out.
Written by the Sig Cox team — NATE-certified HVAC specialists serving the Central Savannah River Area since 1926, with nearly 100 years of experience diagnosing and repairing heat pump systems across Aiken, North Augusta, Augusta, and surrounding communities.
To schedule an inspection or get a straight answer about your system, contact Sig Cox at sigcox.com.
