Discovering ice coating your outdoor air conditioning unit during a Grand Rapids summer is unsettling—and for good reason. While you expect ice in your freezer, finding it on your cooling system is a clear indication that something is seriously wrong. It might seem counterintuitive for an appliance designed to cool air, but this frozen buildup is one of the most serious warning signs your AC can give you. Ignoring it won't make it go away; in fact, it significantly increases the risk of damage, inefficiency, and a complete system failure.
As your trusted, family-owned HVAC experts in the Grand Rapids area, Pro-Tech Heating & Cooling wants to explain why this occurs and why you should call us immediately when you see it.
The Science Behind a Frozen AC Unit
The key principle of air conditioning involves refrigerant cycling through the system. During this process, the refrigerant absorbs heat from your indoor air at the evaporator coil and releases it outside at the condenser unit. The formation of ice, usually on the evaporator coil (inside) or the copper lines outside, is almost always caused by one of two major issues: a lack of airflow or a problem with the refrigerant level.
Issue 1: Restricted Airflow
The most common reason for ice is simply poor airflow across the indoor evaporator coil. The coil gets extremely cold as the refrigerant absorbs heat. If warm indoor air cannot move across the coil fast enough, the coil's surface temperature drops below freezing, causing the condensation that naturally forms on the coil to turn into ice. The main culprits for restricted airflow include:
A Clogged Air Filter: This is the easiest fix, but often the source of the problem. A dirty filter blocks the flow of warm air necessary to keep the coil temperature above freezing.
Closed Vents or Blocked Returns: Closing too many registers or blocking cold air return vents in your home starves the system of the air it needs to exchange heat properly.
Blower Motor Malfunction: A failing blower fan inside your furnace/air handler won't move air with enough force, leading to the same freezing issue.
Issue 2: Low Refrigerant Charge
If airflow is fine, the problem is likely a refrigerant leak. Refrigerant is the substance that absorbs and releases heat; it is not "used up" like gasoline, so if your levels are low, it means there is a leak somewhere in the sealed system. Low refrigerant pressure causes the evaporator coil to absorb too much heat, dropping its temperature dramatically—often well below freezing—resulting in ice formation. A leak not only damages the unit but also releases greenhouse gases, which is why federal regulations require professional repair.
The Dangers of Ignoring a Frozen Coil
When you see ice on your AC in Grand Rapids, do not just wait for it to melt. Continued operation with ice buildup is highly damaging to your system’s most vital components.
First, the ice acts as an insulator, blocking all remaining heat absorption and making the entire unit run uselessly, driving up your energy bills. Second, as the ice melts, the excess water can overflow the condensate drain pan, leading to water damage inside your home, often in the attic or utility room. Third, and most critically, operating the unit while frozen can cause the liquid refrigerant to return to the compressor—a phenomenon known as slugging—which can destroy the most expensive component of your AC system and force an expensive replacement.
What to Do When You See Ice
When ice appears, take these steps immediately: Turn off the unit at the thermostat and set the fan to the "on" position to help melt the ice faster. Check and replace your air filter if it is dirty. Once the ice is completely melted, do not restart the unit. Call Pro-Tech Heating & Cooling at (616) 303-7436 immediately. Our licensed technicians will diagnose the true cause, whether it’s a simple airflow fix or a complex refrigerant leak repair, ensuring your system operates safely and efficiently throughout the West Michigan summer.
