AC Freezing Guide

AC Freezing or leaking

is a common issue that happens for a variety of reasons, including restricted airflow, low refrigerant, weak or failing compressor & a variety of other issues; The good news is that in the majority of cases, it’s caused by a dirty air filter.

If you’ve noticed water around your furnace, indoor coil, or copper pipes that lead to your AC, we recommend you follow these steps:

  1. Turn Off Cooling in Your Thermostat

    If the AC is freezing, it means the system is disrupted and causing the evaporator coil to cool the refrigerant too much and ice over. On your thermostat, turn off cooling & fan on On to allow the system to defrost while you determine the issue.

  2. Check the Air Filter

    As the system defrosts, check the air filter. Dirty filters commonly cause freezing as a dirty or old filter can be cause airflow restriction and lead the ac system to freeze.

    • Single or Multi-family home

      The air filter enclosure is typically located next to the furnace or air handler which is typically a rectangular metal box that stores the furnace’s fan and motor.

      The filter can be placed in an external filter box or inside the furnace or air handler. External filter boxes are typically placed on the bottom of the furnace or air handler. Your furnace or air handler may be in a basement, crawlspace or attic.
    • Apartment or condo

      The air filter is typically in a return duct vent on the ceiling, wall, or floor with slanted openings for air to flow.


      If the filter was dirty

    • Determine the correct filter size noted on the filter itself for the replacement filter. If you are still uncertain, measure the height and width with a tape measure.
    • Dispose of the dirty filter.
    • Follow the instructions printed on the package of the replacement filter to insert it. Arrows should show the direction that the air pulls; the air should be pulled into the system, not away from it.
    • After replacement, keep cooling off & fan on On (in your thermostat) for at least 6-12 hours until the ice has completely de-thawed. Please note that the ice may be inside the indoor coil & not visible, so ensure you have given it a long enough period. In extreme cases, de-thawing may take as long as 24
    • Turn the system back on & see if cooling functionality is normal. If so, you’re good to go.
    • We recommend checking the system every 12 hours after filter replacement to ensure freezing is not happening again for at least one day.
    • If freezing re-occurs, your system may have an issue & needs to be professionally inspected.
    • Please note that consistent freezing will dramatically reduce a unit’s lifespan & can lead to rust & other structural damage that can become safety hazards over time.

*Air filters in an average single-family home should be changed every 30 to 35 days in the summer and every 40 to 60 days in the winter. If you have a pet or a dusty property, air filters may need to be changed more frequently.

      If the filter was not dirty

  • Skip to step 3.
  1. The filter wasn’t the problem

    and the AC system is still not working right, you can try to pinpoint the issue. To determine the source of the problem which will help determine the type of service you need, check the following items:

  • Is the furnace blower working (air coming out of the vents)? If so, check the outdoor unit.
  • Is the outdoor AC unit turning on? There should be a minor hum (compressor) as well as the fan spinning (fan motor). In addition, hot air should be coming out of the unit consistently. If not, your system needs to be checked ASAP. Keep cooling off until it is checked.


These tips are common advise & may be helpful to restore cooling in your home if the freezing was caused by a dirty filter.

However, freezing may happen for a variety of reasons such as low refrigerant, leaks in the indoor coil or outdoor condenser, dirty indoor coil or outdoor unit & therefore if the system continues to have no cooling capacity, it has to be professionally inspected.


You are in good hands – UniColorado Heating & Cooling services thousands of ACs a year; we deal with AC Freezing all the time and can get your systems up and running as quickly as possible.

Schedule a service today with UniColorado Heating & Cooling
Experts You Can Trust at 303-997-0097


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