What to Do If Your AC Is Blowing Warm Air After a Tornado in St. Louis

Your AC unit may blow warm air after a tornado due to power interruptions, damage to components like the compressor or condenser coil, misaligned parts, or refrigerant leaks. To restore cool air, you should immediately verify your power supply, check thermostat settings, inspect filters and coils, look for visible damage, and, if needed, seek professional HVAC help.

 

Check Power Supply and Circuit Breakers

 

Electrical surges or outages during a tornado can trip breakers or blow fuses, cutting power to your air conditioner.

• Locate your home’s electrical panel (breaker box) and look for any switches in the “off” position or in between “on” and “off.”
• Flip any tripped breaker fully to “off” and then back to “on.”
• If your AC still isn’t getting power, check the outdoor disconnect switch near the condenser unit and reset it if needed.
• If a fuse is blown, replace it with one of the same amperage.

If you’re in St. Louis or Nashville, tornadoes can frequently damage outdoor AC components, so always start with the basics.

 

Verify Thermostat Settings

 

Your thermostat controls your cooling system. A misconfigured thermostat can make the unit blow warm air.

• Set the thermostat mode to “cool” rather than “heat” or “off.”
• Adjust the desired temperature at least 2–3 degrees below the current room temperature.
• Ensure the fan setting is on “auto.” If it’s set to “on,” the fan will run continuously without cooling.
• Replace thermostat batteries if you see a low-battery indicator or if the display is dim.

 

Inspect and Replace Air Filters

 

Dirty or clogged air filters block airflow, causing warm air and strain on your system.

• Turn off the AC unit before removing the filter.
• Pull out the filter and hold it up to the light. If you can’t see light through it, it needs replacement.
• Purchase a replacement filter matching the size stamped on the old one (e.g., 16x25x1) from a hardware store.
• Insert the new filter with the airflow arrow pointing toward the indoor unit.

Regular filter changes (every 1–3 months) keep air flowing freely.

 

Examine the Outdoor Condenser Unit

 

The condenser unit dissipates heat from your home. Tornado debris or high winds may damage it.

• Turn off power at the electrical panel and outdoor disconnect first.
• Clear away leaves, branches, and debris around the unit for at least two feet of clearance.
• Inspect the fan and coils for bent fins, dents, or crushed components. Gently straighten bent fins with a fin comb if available.
• Check that the fan motor spins freely by turning the blades by hand; it should turn smoothly without grinding noises.

 

Look for Refrigerant Leaks

 

Refrigerant absorbs heat inside your home. A leak will reduce cooling capacity and cause warm air.

• Look for oily stains around copper refrigerant lines, valves, or coil connections.
• Listen for hissing or bubbling sounds near the outdoor unit, which indicates escaping refrigerant.
• Low refrigerant pressure triggers the AC to lock out; if you suspect a leak, do not add refrigerant yourself.

Only a licensed HVAC technician should repair leaks and recharge refrigerant due to environmental and safety regulations.

 

Assess Ductwork and Vents

 

Tornado-force winds can dislodge ductwork or cover vents with debris.

• Inspect accessible ductwork in the attic or basement for holes, disconnections, or crushed sections.
• Seal small duct leaks with HVAC-approved foil tape or mastic sealant.
• Ensure all supply and return vents inside the house are open and free of obstruction (furniture, drapes, etc.).

Properly sealed and open ducts ensure cool air reaches every room.

 

Listen for Unusual Noises

 

Strange sounds can reveal problems:

• Rattling or banging may mean loose panels or debris inside the unit.
• Squealing often indicates a worn belt (in older systems) or failing fan motor bearings.
• Grinding can signal damaged compressor parts or motor issues.

Document noises and timing to help your technician diagnose the issue faster.

 

Reset the System

 

A simple reset can clear electronic faults:

• Turn off the AC at the thermostat, then shut off power at the breaker and outdoor switch.
• Wait five minutes to let the system’s capacitors discharge.
• Restore power and turn the thermostat back to “cool.”

If the system resumes normal operation, monitor it for consistent performance over the next hour.

 

Call a Professional HVAC Technician

 

If warm air persists after these checks, call a trained technician.

• Look for professionals with NATE (North American Technician Excellence) certification.
• Ensure the company is licensed and insured in your state.
• Ask for a written estimate before any repairs.
• Inquire about warranties on parts and labor to protect your investment.

A certified technician has the tools and expertise to safely diagnose complex issues—like compressor damage or major refrigerant leaks—ensuring your system returns to peak performance.