An AC that won't turn on during a heat wave is stressful — but sometimes the fix is something you can handle in two minutes. Work through this checklist before calling a pro.
1. Check the thermostat
Make sure it's set to COOL (not "off" or "heat") and a few degrees below the current room temperature. If the screen is blank, replace the batteries — a dead thermostat is a common, easy fix.
2. Check your breakers
Your AC has breakers in your electrical panel — often a separate one for the outdoor unit and the indoor blower. A tripped breaker is common. Flip it fully off, then back on. If it trips again immediately, stop — that's an electrical issue for a pro.
3. Check the drain safety switch
Many systems have a float switch that shuts the AC off when the drain pan fills with water. If your drain line is clogged, the AC won't run. Our guide on AC water leaks covers how to clear it.
4. Check the furnace switch and panel
Your indoor unit has an on/off switch nearby that looks like a light switch — sometimes it gets flipped by accident. Many blowers also won't run if the access panel isn't fully closed.
5. Look and listen at the outdoor unit
If the indoor fan runs but the outside unit is silent, or you hear a hum with no start, you may have a failed capacitor or contactor — a common, quick repair.
Still nothing? We'll get you running
If you've checked the basics and your AC still won't start, it's time for a technician. Thermo Master offers 24/7 AC repair across Palatine and the northwest suburbs — give us a call and we'll diagnose it fast.