InglewoodHeating & Air
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Homeowner guide · Cooling

Frozen AC Coil or Leaking Water: What to Do

Ice on an air conditioner in summer looks strange, and water on the floor by the furnace is alarming. The two are often connected. This guide explains why, how to thaw a frozen system without damaging it, how to work out where water is coming from, and when the cause needs a technician.

If you see iceIf you see water

Diagram of an indoor AC coil on top of a furnace: frost on the coil, a drain pan beneath it with a float switch, a primary drain line with a trap running to a household drain, and a secondary drain line running to an outside wall above a window. 1 2 3 4 5 6
  • Indoor (evaporator) coil
  • Drain pan
  • Float switch
  • Primary drain line and trap
  • Secondary drain outlet
  • Blower

Why ice and water often show up together

While it cools, your AC's indoor coil pulls moisture out of the air. That water drips into a drain pan and runs away through a drain line. Normally the coil stays cold but above freezing.

If too little air moves across the coil, or the refrigerant charge is off, the coil can drop below freezing and the moisture turns to ice. When the system stops and the ice melts, it releases far more water at once than usual, and that can overflow the pan. A blocked drain line can cause a leak on its own, with no ice at all.

If you see ice

How to thaw a frozen AC safely

Ice on the copper lines outside or on the indoor coil means the system should stop cooling until it's thawed.

  1. Turn the cooling off

    Set the thermostat to Off. Running a frozen system can damage the compressor.

  2. Run the fan, if it works normally

    Setting the fan to On moves room air across the coil and speeds up thawing. If the blower isn't working properly, leave the system off instead.

  3. Get ready for the meltwater

    Put towels down around the indoor unit and keep an eye on the drain pan area. A lot of water can come off a frozen coil.

  4. Let it melt on its own

    Don't chip or scrape the ice, and don't aim a hair dryer or heater at the coil. The fins and tubing are easy to damage. Light frost may clear in an hour or so; heavy ice can take many hours.

  5. Check the filter and vents meanwhile

    Replace a clogged filter and open any closed vents. Those are the airflow causes a homeowner can fix.

  6. Restart and watch

    Once the coil and lines are fully thawed and dry, switch back to cooling. If ice forms again, turn it off and get a diagnosis.

If you see water

Where the water is coming from, and what it means

Pooling around the furnace or air handler

This can mean the drain pan is overflowing, because the drain line is clogged, the pan is cracked, or ice has melted faster than the drain can handle. Turn the cooling off to stop adding water and mop up. A clogged drain line is best cleared by a technician, especially where it runs through walls or the attic.

Dripping from a pipe outside, above a window

Some systems have a secondary drain that ends somewhere you'll notice it. Water from that outlet is a warning that the main drain is blocked and the backup is doing its job. Have the main drain cleared before it overflows too.

A stain on the ceiling below an attic unit

With equipment in the attic, overflow can reach the ceiling. Turn the cooling off and get it looked at promptly; water damage grows the longer it runs.

The system keeps shutting off

On many systems, a float switch in the pan or drain line stops the cooling when water backs up. It's protecting your home. If the cooling won't restart, the drain or pan usually needs attention; the switch shouldn't be bypassed.

A small pump that's stopped

Where the drain can't flow downhill, a condensate pump lifts the water out. Check that it's plugged in. If it's plugged in and not running, or its reservoir is full, have a technician check it.

What you can do, and what to leave to a technician

You can safely

  1. Turn the cooling off and let the system thaw.
  2. Replace the air filter and open blocked vents.
  3. Put down towels and dry the area around the unit.
  4. Check that a condensate pump is plugged in.
  5. Note where the water or ice is, to describe it when you call.

Leave to a technician

  • Checking or adding refrigerant
  • Opening panels to reach the coil or electrical parts
  • Bypassing or disconnecting a float switch
  • Clearing a drain line inside walls or the attic

When it keeps happening

Why repeated freezing needs a diagnosis

If a clogged filter was the cause, a new filter and a full thaw usually solve it. If the coil freezes again with a clean filter and open vents, the cause is likely something you can't check yourself, such as a blower problem, a dirty coil, a duct restriction, or a refrigerant charge that's off, which usually means a leak.

Each of those needs measuring, not guessing. If the air was simply warm without any ice, start with the not-cooling checklist instead.

What an AC repair visit involves

Ice back again, or water still coming?

Describe what you're seeing. No obligation to hire.

Call (310) 424‑7490