Window Air Conditioner Not Working: Troubleshooting Guide

If your window air conditioner is not working, this expert troubleshooting guide will help you quickly identify the problem and find the right fix.

When a window or room air conditioner stops working properly, the issue usually falls into a few common categories: it doesn’t cool, won’t turn on, leaks water, or makes unusual noise.

This guide will help you diagnose the problem quickly and direct you to the exact fix.

If you’re dealing with a central system instead, see why a central AC isn’t cooling.

Start Here: Identify the Problem

If you’re not sure what’s wrong, start by matching your symptoms:

• AC runs but doesn’t cool: See Window AC Not Cooling →
• AC won’t turn on at all: See Window AC Not Turning On →
• Water leaking inside: See Window AC Leaking Water →
• AC making noise: See “Making Noise” below

Start With These Quick Checks

Before diving into detailed troubleshooting, try these basic checks:

• Make sure the unit is plugged in and receiving power
• Set the thermostat to “Cool” and below room temperature
• Check that the filter is clean
• Make sure room doors and windows are closed

These simple fixes solve many common problems.

Common Window AC Problems & Fixes

Some issues—like dirty filters or airflow problems—also affect whole-house systems. Learn how to change an AC filter or why an AC can’t reach temperature.

Window AC Not Cooling

If your air conditioner runs but doesn’t cool the room, the problem is often related to airflow or maintenance.

Common causes include:

• Dirty air filter or coils
• Blocked airflow
• Low refrigerant

👉 See full step-by-step cooling fixes →

Window AC Not Turning On

If the unit doesn’t start at all, the issue is usually electrical.

Common causes include:

• Power supply problems
• Tripped circuit breaker
• Faulty thermostat or switch

👉 See full electrical troubleshooting steps →

Window AC Leaking Water

If water is dripping from your AC unit inside your home, the issue is usually related to proper drainage or installation of the unit.

Common causes include:

• Clogged drain holes
• Improper tilt
• Dirty filter causing ice buildup

👉 See full water leaking fixes →

Window AC Making Noise

Unusual noises usually indicate mechanical problems or loose components.

Common causes include:

• Loose mounting or parts
• Debris inside the unit
• Worn fan motor or bearings

If tightening and cleaning don’t solve the issue, the unit may need professional repair.

Should You Repair or Replace the Unit?

Not every air conditioner is worth repairing.

Consider replacing the unit if:

• It is more than 10 to 15 years old
• Repair costs are high
• Performance has steadily declined

Newer models are often more energy efficient and quieter.

👉 See Room Air Conditioner Buying Guide →

FAQs: Window Air Conditioner Not Working

Why is my window air conditioner not working?

Most problems fall into a few categories: lack of cooling, electrical issues, drainage problems, or mechanical failure. Identifying the symptom is the first step to finding the solution.

What is the most common AC problem?

The most common AC issue is reduced cooling caused by a dirty filter or restricted airflow.

Can I fix a window air conditioner myself?

Many common problems—such as cleaning filters, clearing drains, or resetting breakers—can be fixed without professional help. More complex repairs may require a technician.

When should I replace instead of repair?

If the unit is fairly old or requires major repairs, replacement is often the better long-term option.

NEXT SEE:

• Window AC Not Cooling
• Window AC Not Turning On
• Window AC Leaking Water
• How Room Air Conditioners Work
• Room Air Conditioner Buying Guide

Back to top