Frozen AC coil traced to an open condensate drain line

Last updated October 27, 2026Reviewed by Waseem Shahzad, Lead Technician

Northport, NYAC RepairTechnicians: Waseem and JustinAugust 2026

No cooling from a frozen indoor coil. An uncovered drain line was drawing air into the unit; we fixed it, let the coil thaw and finished the next morning.

Outdoor air conditioning equipment beside a Northport home

Outdoor condenser checked on a no-cooling call, Northport NY

Refrigerant scale used to add a measured charge, Northport NY

Manifold gauges reading system pressures after the repair, Northport NY

What the homeowner reported

The homeowner reported that the air conditioning was not working and the house was not cooling.

What we found

The indoor coil was frozen. The condensate drain line running to the condensate pump had no cover, so the negative pressure inside the unit was pulling air back through the drain, which helped the coil freeze.

What we did

The team fixed the open drain line and let the ice melt completely before checking pressures, since a frozen coil gives false readings. They came back the next morning, found the system low on refrigerant and added 2 lb of R-410A.

Visits and time on site

Two visits: the first to diagnose and thaw the coil, the second the following morning to check pressures and charge the system.

The result

After the charge was added, the air conditioning was working properly and everything else checked out.

Job details are from our August 2026 service record for this Northport home. Customer details are left out.

General information, not details from this job

About frozen coils and drain lines

An indoor coil freezes when too little warm air crosses it or the refrigerant runs too cold. The usual suspects are a dirty filter, low refrigerant or an airflow problem, and an open drain connection can make it worse by letting air leak into the cabinet. The ice has to melt before pressures mean anything, which is why a frozen system often takes two visits.