Top AC Problems in Cold Weather and How to Fix Them Quickly

When the temperature drops, most people shift their focus from air conditioning to heating. But even in the off-season, your AC system can encounter issues that—if ignored—may lead to costly repairs when summer returns. Just because your AC isn’t actively cooling doesn’t mean it’s immune to damage.

Understanding the most common air conditioning problems in winter, why they happen, and how to fix them can help you maintain a reliable, energy-efficient system year-round.

1. Frozen AC Coils and Lines

Why it happens:

Even when your AC is off, moisture from rain, snow, or condensation can settle on coils or refrigerant lines. In freezing temperatures, this moisture can solidify, causing ice buildup that damages key components.

How to fix it:

• Insulate exposed refrigerant pipes with foam sleeves to prevent freezing.

• Avoid running your central air conditioning system during cold weather unless it’s a heat pump designed for winter use.

• If coils are already frozen, turn the system off and allow it to thaw. Do not try to chip away the ice.

2. Rodents or Debris Inside the Unit

Why it happens:

During the colder months, outdoor AC condenser units are idle, making them an inviting home for rodents, birds, or insects. Nesting and debris can block airflow and chew through wires.

How to fix it:

• Use a breathable, waterproof AC cover to protect the unit without trapping moisture.

• Inspect the unit monthly during winter.

• If animals have nested inside, call an HVAC technician to check for internal damage before restarting the system in spring.

3. Electrical Issues from Moisture Exposure

Why it happens:

Snow, rain, and condensation can creep into vulnerable parts of your air conditioning unit, especially if it’s not properly sealed or elevated off the ground. This may lead to short circuits or corrosion on electrical contacts.

How to fix it:

• Shut off power to the AC from the breaker panel during winter.

• Schedule a pre-season HVAC inspection to test electrical components before turning the system back on.

• Ensure proper drainage and clear snow from around the base of the unit.

4. Clogged Drain Lines and Mold Growth

Why it happens:

Standing water in the AC condensate drain line can freeze, clog, or promote mold and algae growth when temperatures fluctuate.

How to fix it:

• Flush the drain line with a mixture of water and vinegar before winter hits.

• Keep the surrounding area dry and clear of debris.

• If the drain line is frozen or clogged, contact a professional to avoid overflow and water damage.

5. Damaged or Disconnected Ductwork

Why it happens:

Inattentive homeowners sometimes forget about their duct system, especially in crawl spaces and attics. Cold air, rodents, or shifting insulation can loosen connections or create leaks.

How to fix it:

• Conduct a visual inspection of accessible ducts or hire an HVAC technician for a full ductwork inspection.

• Seal minor leaks with aluminum tape (not standard duct tape).

• Insulate exposed ductwork to protect it from cold temperatures.

The Role of Preventative Air Conditioning Maintenance

Most cold-weather AC problems can be avoided with routine air conditioning maintenance. Just because your system is dormant doesn’t mean it should be neglected.

Here’s what an off-season maintenance checklist might include:

• Cleaning and inspecting the outdoor condenser unit

• Wrapping refrigerant lines with weather-resistant insulation

• Clearing leaves, snow, or dirt from around the unit

• Testing electrical components for corrosion or wear

• Ensuring the thermostat and HVAC system are properly programmed

A seasonal tune-up not only prevents breakdowns—it extends the life of your system and ensures efficient performance when you need it most.

Bonus Tip: Consider a Heat Pump System

If your HVAC system includes a heat pump, it likely runs year-round, even in winter. These systems are designed to both heat and cool, but they still need maintenance to avoid defrost cycle malfunctions or refrigerant issues in cold weather.

If you notice your heat pump freezing or struggling to keep up, schedule a service call before it escalates into a bigger problem.