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:
- Replace batteries (if battery-powered)
- Check if the circuit breaker for the thermostat/furnace is on
- 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?