Safe Homeowner Checklist
- 1Set the thermostat to Cool and lower the setpoint below the room temperature.
- 2Replace thermostat batteries if the screen is blank, dim, or acting strangely.
- 3Wait five to ten minutes if the thermostat shows a delay or compressor protection message.
- 4Listen for the indoor blower and look outside to see whether the outdoor unit starts.
- 5Check for water near the indoor unit that may point to a drain safety switch.
- 6If safe and clearly labeled, reset the AC breaker once. If it trips again, stop.
Call a Technician If...
- The thermostat is on Cool but neither indoor nor outdoor equipment starts.
- The indoor blower runs but the outdoor unit does not.
- The breaker trips again after one safe reset.
- You see water near the indoor unit or the drain pan looks full.
- You hear buzzing, clicking, or humming from equipment that does not start.
- You are unsure which breaker or switch controls the system.
Indoor vs outdoor tells the story
If nothing runs, the issue may be thermostat, power, controls, or a safety switch. If the indoor blower runs but the outside unit does not, the cooling side needs technician diagnosis.
This distinction helps you describe the problem clearly when you call or text for service.
Condensate safety switch symptoms
Many systems have a float switch that can shut cooling off when the drain backs up. This helps prevent ceiling, wall, or floor damage.
Do not bypass the switch. If water is present or the system shuts off again, the drain line and safety switch need service.
When This Becomes Repair vs Replacement
A no-start problem is often repairable if it is a thermostat, control, drain safety, or single electrical component issue on an otherwise healthy system.
Replacement should be discussed if the no-start diagnosis points to major compressor failure, repeated electrical failures, or a very old system with poor comfort and high repair history.
Do not approve major repairs without also understanding the age of the system and what replacement would solve.