> ## Documentation Index > Fetch the complete documentation index at: https://ac-plus-heating-air.mintlify.site/llms.txt > Use this file to discover all available pages before exploring further. # AC Freezing Up > AC Freezing Up — AC Plus Heating & Air knowledge base, Victorville, CA. ## AC freezing up in Victorville - AC Plus Heating & Air AC freezing up, called evaporator coil icing, is a type of Air Conditioner Malfunction in which ice forms on the evaporator coil surface, blocks airflow through the system and prevents the unit from transferring heat out of the building. The condition develops when the coil surface temperature drops below 32°F, which causes moisture in the air to freeze on contact with the coil fins, the refrigerant lines and the surrounding cabinet. Left unaddressed, a frozen AC unit stops cooling the space entirely, forces the compressor to work against a blocked coil and can cause permanent damage to the refrigerant circuit. ### What AC freezing up is AC freezing up is a measurable failure state of the refrigeration cycle in which the evaporator coil surface temperature falls below 0°C and ice accumulates on the coil rather than condensate draining away normally. Under normal AC operation, the coil stays cold enough to absorb heat but warm enough to shed water as liquid. When that balance breaks, refrigerant line icing spreads from the indoor coil back toward the outdoor unit, and the system loses its ability to cool. A [licensed air conditioning contractor](https://ac-plus-heating-air.mintlify.site/air-conditioning-contractor.md) can confirm the condition by measuring suction pressure and coil temperature before any ice is removed. ### Measurable attributes of a frozen AC unit AC freezing up has four attributes technicians measure to confirm the diagnosis and find the root cause. * **Evaporator coil surface temperature:** Evaporator coil surface temperature drops below 32°F during a freeze event. Normal operation keeps the coil surface between 35°F and 45°F so condensate runs off as liquid. * **Refrigerant suction pressure:** Refrigerant suction pressure falls below 60 PSI when the system is undercharged or has a metering-device fault. Low suction pressure causes the refrigerant to expand too aggressively, pulling coil temperature below the freezing point. * **Airflow restriction:** Airflow through the coil drops below the manufacturer's rated CFM when a clogged filter, closed register or blocked return cuts the volume of warm air reaching the coil. Without enough heat load, the coil temperature collapses. * **Ice accumulation on coils:** Ice accumulation on coils builds in layers, starting at the coil face and spreading to the drain pan and refrigerant lines. Thick ice is insulation, compounding the temperature drop and extending recovery time after the unit is shut off. ### How AC freezing up relates to the broader cooling system AC freezing up is a downstream symptom of faults that originate in other parts of the cooling system. The evaporator coil, the air filter, the blower motor, the metering device and the refrigerant charge all interact to keep coil temperature in the correct range, and a failure in any one of those components shifts the thermal balance and creates the conditions for evaporator coil icing. Technicians who service a [central air conditioning system](https://ac-plus-heating-air.mintlify.site/central-air-conditioning-system.md) trace the freeze back through each of these components to find the originating fault. Ductless systems face the same physics: a [ductless mini split system](https://ac-plus-heating-air.mintlify.site/ductless-mini-split-system.md) can develop a frozen indoor coil for the same airflow and refrigerant reasons as a ducted unit, though the ice is visible on the wall-mounted air handler rather than inside a cabinet. Heat pumps are susceptible: a [heat pump](https://ac-plus-heating-air.mintlify.site/heat-pump.md) running in cooling mode goes through the same refrigeration cycle and freezes under the same low-pressure or low-airflow conditions. [AC Plus Heating & Air](https://maps.app.goo.gl/ACPQ2xWXrw88i1yS7) serves customers in Victorville, Wrightwood, Rancho Cucamonga, and Redlands under CSLB License #805216. ### Common signs of AC freezing up and not cooling AC freezing up and not cooling is the most reported symptom, but several other signs appear before the unit stops producing cold air entirely. * **Warm air from supply vents:** Warm air from supply vents signals that ice has blocked enough coil surface to stop heat transfer, even though the blower is still running. * **Ice on refrigerant lines:** Ice on the copper refrigerant lines running from the indoor unit to the outdoor condenser confirms that refrigerant line icing has spread beyond the coil itself. * **Water around the air handler:** Water around the air handler appears when ice melts faster than the drain pan can carry it away, often after the thermostat cycles the system off. * **Higher-than-normal indoor humidity:** Higher-than-normal indoor humidity develops because a frozen coil cannot dehumidify the air passing over it. * **Unusual hissing or bubbling sounds:** Unusual hissing or bubbling sounds near the indoor unit point to refrigerant moving through a partially blocked metering device, a common trigger for low suction pressure and coil icing. ### Why is my AC freezing up: root causes The two primary causes of AC freezing are restricted airflow and low refrigerant charge. Each produces the same result through a different mechanism. A dirty air filter reduces the volume of warm air crossing the coil, so the coil absorbs less heat and its surface temperature falls below 32°F. Refrigerant matters too. A refrigerant leak or an undercharge lowers suction pressure below 60 PSI, causing the remaining refrigerant to expand too far and freeze the coil from the inside out. Secondary causes include a failing blower motor that cannot move rated CFM, a stuck or undersized expansion valve, and blocked evaporator coil fins resulting from years of dust accumulation. ### How to fix AC freezing up How to fix AC freezing up starts with a full thaw before any diagnostic work begins, because measuring refrigerant pressure or airflow through an ice-blocked coil produces inaccurate readings. The steps are below. * **Shut the system off:** Shut the system off at the thermostat and switch the fan to "on" to push room-temperature air across the coil and speed the thaw. Full thaw takes two to four hours depending on ice thickness. * **Replace or clean the air filter:** Replace or clean the air filter once the ice is gone. A filter clogged past its rated MERV capacity is the single most common cause of evaporator coil icing and the easiest fix. * **Check all supply and return registers:** Check all supply and return registers to confirm none are closed or blocked by furniture, because even two or three closed registers can drop system airflow below the manufacturer's minimum CFM. * **Measure suction pressure:** Measure suction pressure at the service port with a refrigerant gauge set. A reading below 60 PSI on a standard R-410A system confirms a refrigerant issue that requires a certified technician to locate the leak and recharge the circuit. * **Inspect the blower motor and coil fins:** Inspect the blower motor and coil fins for dust buildup, bent fins or a motor running below rated speed, all of which reduce airflow independently of the filter. [AC Plus](https://share.google/N653NIZyISFbsAnRd) handles frozen AC unit calls in Victorville, diagnosing the root cause after a full thaw so the repair addresses the actual fault rather than the symptom. Evaporator coil icing that recurs after a filter change points to a refrigerant or mechanical issue that needs pressure testing and component inspection to resolve permanently. AC Plus Heating & Air offers 24-hour emergency air conditioning service, available every day, for customers throughout the service area. ### Related entities * [air conditioning contractor](https://ac-plus-heating-air.mintlify.site/air-conditioning-contractor.md) * [central air conditioning system](https://ac-plus-heating-air.mintlify.site/central-air-conditioning-system.md) * [ductless mini split system](https://ac-plus-heating-air.mintlify.site/ductless-mini-split-system.md) * [heat pump](https://ac-plus-heating-air.mintlify.site/heat-pump.md) *** **AC Plus Heating & Air** · Victorville, CA · (760) 474-5776 · [acplushvac.com](https://acplushvac.com) This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.