Start with the thermostat
Make sure it is set to Cool, not Heat or Fan On, and set a few degrees below room temperature. Replace the batteries if the screen is dim or blank.
Check the filter and breakers
A clogged filter can starve the system of air and freeze the coil. Replace it if it looks gray.
Check the AC breaker in your panel and the disconnect switch beside the outdoor unit.
Look at the outdoor unit
The fan should be spinning and the unit should be clear of cottonwood fluff, leaves and grass. If it hums but the fan doesn't spin, turn it off and call us; that is often a failed capacitor.
Watch for ice
Ice on the copper lines or indoor coil means turn the AC off and run the fan only until it melts. Then call, because ice usually points to an airflow or refrigerant problem.
When to call
If the checks above don't fix it, call Townsend Mechanical at (719) 659-4648 or book online. We test the electrical parts, refrigerant charge and airflow and quote the repair before starting.
Safety reference: CDC carbon monoxide safety guidance.