Help! My A/C Lines Are Frozen – What Should I Do?

If you’ve gone outside and noticed that the copper lines on your air conditioner are covered in ice or frost, you’re not alone. This is a common issue, especially during Colorado’s hot summer days. But while it might look harmless, frozen A/C lines are a sign that something’s not working right—and using your system while it’s frozen can make things worse.

Here’s what to do right away if your A/C lines are frozen, and how to prevent it in the future.

Step 1: Turn Off Your A/C

As soon as you notice ice on the lines outside, or even water or ice near your indoor unit (like the furnace or coil area)—shut off your air conditioner at the thermostat. Continuing to run it while frozen can cause major damage to the system, especially the compressor.

Step 2: Set the Thermostat to “Fan On”

Once cooling is turned off, set your thermostat fan setting to “On” (not “Auto”). This runs just the blower, helping warm air move over the frozen coils and speed up the thawing process. Do not turn the cooling function back on yet, only the fan.

Step 3: Check Your Air Filter

A clogged or high-efficiency (high-MERV) filter can restrict airflow and cause the evaporator coil to freeze.

• Pull the filter and inspect it

• Replace it if dirty or if you recently switched to a high-MERV filter

• We recommend changing filters regularly and avoiding filters rated above MERV 11 unless your system is designed for them

Step 4: Inspect Air Vents and Returns

Blocked vents, closed registers, or dirty return grills can also restrict airflow and cause freezing.

• Make sure all supply vents are open

• Check that nothing is covering them (like furniture or rugs)

• Wipe down dusty return air grills to improve circulation

Step 5: Let the System Thaw Completely

Depending on how much ice has built up, it can take several hours to fully defrost. Be patient and do not try to scrape off the ice or melt it with hot water. You may also notice water pooling near your indoor unit; this is normal during the thawing process, but it’s a sign that ice has reached the indoor coil area. Lay down towels if needed.

Step 6: Call for Service

Once the system is fully thawed, don’t turn the A/C back on just yet. A frozen system means something isn’t working right and running it again can cause another freeze-up or lead to permanent damage. Instead, contact a licensed HVAC professional (like us!) to inspect the system, pinpoint the cause, and safely get it cooling again.

Why Do A/C Lines Freeze?

Here are the most common reasons we see A/C systems freeze up:

• Dirty or clogged air filters

• High-MERV filters restricting airflow

• Low refrigerant (often due to a leak)

• Dirty evaporator coils

• Blower motor problems

• Blocked or undersized ductwork

• Thermostat set too low (we recommend 72°F or higher)

• Poor system design or airflow imbalance

 Most of these issues require professional diagnosis—but catching and fixing them early can save you from more expensive repairs later.

 Need Help? We’ve Got You Covered.

At Pendleton Heating & Cooling, we know how uncomfortable and stressful a frozen A/C can be. If your system is iced up, we’re just a phone call away. Call us today or schedule online for expert service and honest, no-pressure solutions. We offer flat-rate pricing and financing options to make repairs or upgrades easier on your budget.