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AC Diagnostic Tool

This tool guides you through common AC problems step by step. Answer each question honestly — the result will tell you whether it's a DIY fix or time to call a professional.

Step 1 of 5

Check the Basics

First, check your thermostat:

  • Is it set to the Auto, Cool, or Heat mode as desired?
  • Is the set temperature appropriate for the season?
  • Does the display turn on?

Does the thermostat display show any activity?

Step 1 of 5

Thermostat Settings

Is the thermostat set to the desired mode and the temperature set appropriately?

Step 1 of 5

Thermostat Power

The thermostat may be dead. Try these:

  1. Replace batteries (if battery-powered)
  2. Check if the circuit breaker for the thermostat/furnace is on
  3. For smart thermostats, check if the C-wire is connected

Did replacing batteries or checking the breaker help?

Step 2 of 5

Check the Circuit Breaker

Locate your electrical panel and look for:

  • A breaker labeled AC, HVAC, Condenser, or Furnace
  • Breakers that are in the middle position (tripped) vs fully ON or OFF
  • DO NOT touch any breaker if you see signs of burning or melting

Is the AC breaker tripped (in the middle position)?

Step 2 of 5

Reset the Breaker

Reset it by flipping fully OFF, then fully back ON. Wait 5-10 minutes for the AC system to restart.

Did the AC start working after resetting the breaker?

Step 3 of 5

Inspect the Outdoor Unit

Go outside and find your condenser unit. Check for:

  • Is the unit running? Listen for the fan and compressor
  • Is the fan spinning freely?
  • Are there leaves, grass, or debris blocking the sides?
  • Is there ice or frost on the copper lines or the unit itself?
  • Is the unit level and on a solid surface?

Is the outdoor unit running (fan spinning, compressor humming)?

Step 3 of 5

Outdoor Unit Sound

Can you hear a humming sound from the unit but the fan isn't spinning?

Step 3 of 5

Outdoor Unit Debris

Is the unit blocked by debris, vegetation, or overgrown bushes?

Step 4 of 5

Airflow Check

The air filter is the single most overlooked cause of AC problems.

Have you checked or replaced the air filter in the last 3 months?

Step 4 of 5

Filter Condition

A dirty filter is the #1 cause of poor cooling. Check it now. Location: usually in the return air grille, furnace cabinet, or in a slot near the thermostat.

Was the filter dirty?

Step 4 of 5

Supply Vents

Are all supply vents (registers) open and unobstructed?

Step 5 of 5

Refrigerant Check

Refrigerant issues show specific symptoms:

  • Ice or frost on the copper lines or outdoor unit
  • Hissing or bubbling sounds from the unit
  • AC runs but never cools enough
  • Higher than normal electric bills

Do you see ice or frost on any AC pipes or the outdoor unit?

Step 5 of 5

Refrigerant Sounds

Do you hear a hissing or gurgling sound near the indoor or outdoor unit?