Photograph of client using tissue to look for air conditioning air flow How to Diagnose & Repair
Iced Cooling or Evaporator Coils
Fix an A/C or Heat Pump system that has ice or frost problems, weak air flow, lost cooling

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Diagnose & fix ice or frost blockage of the cooling coil or evaporator coil in an air conditioning / heat pump system. We explain the causes of cooling coil ice formation and blockage. Some of these causes can be repaired by something as simple as changing a dirty air filter or cleaning a dirty coil or blower fan.

We discuss simple checks you can make that may avoid a costly service call if your air conditioner is not working. . This article forms part of our series on how to diagnose an air conditioner or heat pump that is not cooling: this article explains how to diagnose and correct air conditioning problems like lost or reduced air conditioner cooling capacity, reduced or no cool air flow, reduced or no actual lowering of the air temperaturer, or an air conditioner that won't start.

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Air Conditioner Cooling Coil Icing Problems & Coil Leaks

Ice blocked air conditioning cooling coil (C) Daniel Friedman

Cooling Coil Ice-Up on the air conditioner air handler or evaporator coil: A second result of the reduced air flow due to a dirty air conditioning filter can cause the evaporator coil (the cooling coil) in the air handler to become blocked by ice, stopping or significantly reducing cool air output from the system.

A visual inspection of the cooling coil in the air handler can quickly show whether or not it's ice-covered. If the coil is iced-up and blocked, turn off the cooling system entirely until the ice has all evaporated and cleared. Be sure that your condensate drain is not blocked and that the water from melting ice will be properly disposed-of.

If you replace all dirty filters on the system and remove ice from an iced coil and the coil ices up again when the system is turned back on, you may have the next condition in this list.

For a detailed discussion of air conditioner or other refrigeration (or dehumidifier) cooling coil ice-up diagnosis and cure, see FROST BUILD-UP on AIR CONDITIONER COILS

Cooling Coil (Evaporator Coil) Leaks, Condensing Coil Leaks: if your A/C system used to work fine but now is blowing only warm air, it is possible that you have lost refrigerant in the system. A refrigerant leak can occur anywhere in the refrigerant piping system, in the cooling coil, or in the condensing coil.

You'll need an HVAC technician to find and repair the leak problem. If the leak is in a refrigerant line it can usually be soldered and sealed and the system re-charged. If the leak is in a cooling coil or condensing coil, the coil probably needs to be replaced. We explain this topic in more detail below at Air Conditioner Refrigerant Problems - Refrigerant Leaks, Low Refrigerant, Wrong Temperatures.


Dirty filter blocks air flow (C) Daniel Friedman

Watch out: something as simple as a blocked or dirty air filter or dirty cooling coil can lead to frost build-up on the cooling coil. That's because the reduced airflow over the cooling coil may permit it to run colder than normal.

Clogged Air Conditioner filters can lead to lost cooling capacity first, because the clogged filter reduces the air flow through the system, meaning that you'll feel less air flow at the supply registers than was previously present, and second because the low air flow may lead to partial or completed frost blockage of the cooling or evaporator coil in the air handler.

See AIR FILTERS for HVAC SYSTEMS for details.

Air Filter problems: not enough air coming out of air conditioning ducts?

Check for a very dirty, blocked air filter or blower fan. See AIR FILTERS for HVAC SYSTEMS and AIR HANDLER / BLOWER UNITS


Continue reading at A/C COOLING COIL ICE FROST for complete diagnosis & repair procedures for coil frosting or icing troubles

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