HVAC Services
AC Not Cooling? 5 Diagnostic Steps Before Calling a Pro
If your central air conditioner is running constantly but your home remains warm, systematic non-invasive checks of your thermostat, filters, outdoor condenser, and condensate drain lines can uncover the root cause.
Non-Invasive Diagnostic Boundary
Homeowners can safely replace air filters, reset breakers, and clear outdoor brush. Do not open the electrical service disconnect box or connect pressure gauges to pressurized refrigerant ports without EPA Section 608 certification.
1. The 5-Step Diagnostic Inspection
Perform these five basic checks before paying an emergency HVAC dispatch fee:
Ensure mode is set to COOL (not FAN or HEAT) and fan is set to AUTO (not ON). Setting fan to ON circulates unconditioned air when the condenser cycles off.
A dirty, suffocated air filter restricts airflow across the evaporator coil, causing weak airflow and eventual coil freeze-ups.
If water backs up in your condensate drain pipe, an overflow float switch will trip to shut down the outdoor condenser and prevent ceiling water leaks.
Look at the outdoor unit. Is the top fan spinning? Are exterior aluminum fins matted with grass clippings, cottonwood, or leaves?
Check your main electrical panel and the outdoor disconnect box to ensure the 30-50 amp compressor breaker has not tripped.
Primary Standard Reference: Air Conditioning Contractors of America (ACCA) Residential Maintenance Guidelines
Frequently Asked Questions
Why is my AC running but blowing lukewarm air?
Common causes include a dirty air filter, a tripped outdoor condenser breaker (running indoor blower only), a failing run capacitor, or low refrigerant charge.
How much does it cost to fix an AC blowing warm air?
A new filter or clearing a condensate drain costs $20-$150. Replacing a capacitor or contactor costs $180-$400. Refrigerant leak repairs cost $450-$1,500.