Why Does My Air Conditioner Freeze Up and Leak Water?

An air conditioner that freezes up or leaks water indoors is one of the complaints that wears down the client relationship the most: it looks serious, it makes a mess and it almost always means a second visit. The good news is that nearly all the causes are connected. Here's how to sort them out.

Why ice forms on the evaporator

Ice appears when the evaporator drops below freezing. Typical causes:

• Insufficient airflow: dirty filter, weak blower or closed vents. The most frequent cause.
• Low refrigerant charge: a leak lowers pressure and the coil overcools until it freezes.
• Dirty coil: a grimy evaporator can't exchange heat well.
• Thermostat or very long cycles: the unit runs nonstop and builds up ice.

Why it leaks water

Some water is normal (condensate), but it becomes a leak when:

• The pan or drain is clogged and water overflows.
• Built-up ice melts suddenly when the unit shuts off.
• The install has no slope, so condensate won't drain.
• The line lacks insulation and sweats externally.

Step-by-step diagnosis

1. Turn the unit off and let it fully defrost before measuring anything.
2. Check and replace the filter; confirm the blower moves air.
3. Measure pressures: if low, find the leak before recharging.
4. Clean the evaporator and condensate pan.
5. Clear the drain and verify it slopes outward.

How to keep the same unit from failing again

The problem isn't clearing a drain: it's that three months later the same client calls about the same thing and no one remembers what was done. When you log every visit with before-and-after photos, the cause you found and the part you used, you turn a recurring complaint into a record that backs up your work and lets you sell preventive maintenance with real arguments.

Frequently asked questions

Why is my AC dripping water inside? Almost always a clogged drain or melting ice. Check the pan and condensate line first.

Is it dangerous to run the AC if it freezes? Yes, it can damage the compressor over time. Turn it off, defrost it and diagnose the cause before running it again.

How often should the drain be cleaned? In humid climates, at least every 6 months as part of preventive maintenance.