Why is my system freezing up?

There are several factors that can cause system freezing. Most need correction by an HVAC professional.

The first thing you can do to prevent or correct your system from freezing up is to ensure the filter is clean or replaced. During that time you can check to see if there is any restriction of airflow.

Dirty filter

After replacing or cleaning the filter, you can speed up the thawing process by turning the system off and turning on the fan. If you have a heat pump system, you can try turning the system to heating mode until the ice has melted. After the ice has melted, switch the system settings back to normal. If the system refreezes, contact your HVAC professional to correct the problem.

Low refrigerant

In some cases, a leak in the refrigerant lines can cause freezing. Some of the factors that can cause leaks are:

  • Weak solder joints
  • Friction from piping rubbing or vibrating against an object
  • Open valves
  • Loose fittings

If leaking is occurring, you need to determine whether to have the system repaired or replaced. The age of the system and the nature and location of the leak are factors in making that decision.

Dirty evaporator coil

Over time, the evaporator coil will become dirty. When this happens, you will begin to lose airflow. This happens over time, so it’s easy to miss. Eventually, it freezes up or compromises cooling performance. At this point, you will need to contact your HVAC technician to correct the problem.

Defective blower motor or relay

A blower motor not running at the proper speed or not running at all is another factor that can cause freezing. The motor operation may be intermittent, starting at full speed and slowing down after it heats up. Or, a relay could cause it to start one time and not the next. In either case, you will need to contact an HVAC technician to correct the problem.