If your AC isn’t turning on when it should, a few steps can help you resolve simple issues and restore cooling to your home. Some problems, such as refrigerant leaks or capacitor failures, require expert HVAC repair. Understand why your AC isn’t turning on with this troubleshooting guide and when to call 1st Choice Mechanical in Phoenix for assistance.
Initial Assessment
Before considering more complex problems, troubleshooting should start with a simple inspection to rule out basic or obvious issues.
Check the power source
Start by checking that the power switches for the indoor and outdoor units are on. Locate your home’s electrical panel and the circuit breaker inside, labeled for your AC. When a breaker trips, the handle moves to the middle position. Reset it by flipping it to the off position and then to the on position.
Inspect the external unit
Inspect the unit for damage, such as dented panels or disconnected wires. Remove obstructions, leaves, dirt, and other debris that have accumulated around it.
Check the control panel
Modern AC units sometimes feature control panels that display diagnostic codes and indicate specific issues. HVAC-integrated smart home systems send error notifications to your mobile device, making it easier to pinpoint the cause of a malfunction. AC brands and models have their own diagnostic codes, which you can find in your owner’s manual.
Thermostat Issues
Since the thermostat controls AC operation, incorrect settings or malfunctions can prevent the system from turning on. Check the thermostat’s display and ensure that it’s set to cooling mode. If the display is blank or unresponsive, replace the batteries or carefully inspect the thermostat for loose or damaged wiring.
Verify the temperature settings by lowering the thermostat to 5 degrees less than the current room temperature to test whether the system responds. If your system doesn’t respond, the thermostat may have a dirty or damaged sensor, inaccurate calibration, or faulty connections to the AC unit.
A simple thermostat reboot may also restore proper AC function. To reset your thermostat, power it off for about 10 minutes, then restart it and adjust the programming as needed. Some models also have a dedicated reset button, while others may require temporarily removing the batteries.
Air Filter and Airflow
Restricted airflow from clogged filters, blocked vents, and other issues increase the risk of AC overheating and safety shutdowns. With weak airflow, ACs must work harder to cool your home, increasing strain and wear on components and potentially leading to failure.
As part of regular AC maintenance, air filters require replacement every 30 to 90 days, depending on your home’s indoor air quality and the presence of dust, pet dander, and other pollutants. Locate the air filter compartment within the HVAC system, usually near the return duct or air handler. With the power disconnected at the breaker, remove the filter and inspect it for excessive dirt. If it’s gray or clogged, replace it with a compatible filter.
Blocked vents can also imbalance airflow and strain your system. Check that air duct vents throughout your home are open and free of obstructions, such as furniture or other belongings.
Condensate Drain and Water Overflow
Your AC system extracts moisture from the air it draws in, and the resulting water travels outside your home via the condensate drain line. Most ACs have a water or condensate overflow safety switch, which shuts the AC off automatically if the pan overflows to prevent damage and safety hazards.
Inspect the drain pan located near the evaporator coils in the indoor unit. Empty the pan if it contains water, and monitor whether your AC resumes normal operation. If the problem persists, follow these steps to troubleshoot the condensate drain line:
- Step one: Disconnect the AC power.
- Step two: Locate the drain and its outlet, usually a PVC or copper pipe with a T-shaped access point. Remove the cap.
- Step three: Remove any accessible debris or blockages with gloves or a wire brush.
- Step four: Use a wet/dry vacuum or plumbing snake for deeper clogs.
- Step five: Flush and clean the line with an approved cleaning solution, such as vinegar and hot water.
Capacitor and Electrical Components
Capacitors, circuit boards, wiring, and other electrical components may degrade over time and prevent the AC system from turning on.
The capacitor provides the initial power needed to start a cooling cycle. A system with a faulty capacitor may struggle to start or fail completely. Since capacitors pose electrical hazards, further inspection should be left to a professional.
Visually inspect AC wiring — if it appears damaged, loose, or otherwise faulty, don’t attempt to repair it. Refer to an HVAC professional to assess and repair electrical connections.
Refrigerant Levels and Leaks
Refrigerant absorbs and transfers heat from the air inside your home. Leaking or insufficiently charged refrigerant limits your AC’s cooling abilities, and many systems have sensors that trigger shutdowns if they detect low refrigerant levels. Look for these signs of refrigerant problems:
- Hissing or bubbling noises
- Warm air from vents during cooling cycles
- Frozen evaporator coils
Refrigerant leaks require specialized equipment and handling. Contact a licensed HVAC professional to repair leaks and recharge the refrigerant.
Mechanical and Component Failures
The compressor, blower fan motor, and other components are integral to your AC system’s proper function, and mechanical or component problems may cause system failure.
The blower fan motor, for example, drives airflow and distributes conditioned air throughout your home. Seized bearings, damaged fan blades, loose parts, and other issues may cause overheating or motor damage. Grinding or screeching sounds, weak airflow, and complete shutdowns often indicate motor failure.
Contact 1st Choice Mechanical for Professional AC Maintenance & Repair
If your AC still won’t turn on despite troubleshooting, professional diagnosis and repair are necessary. Many AC problems, especially those related to refrigerant, electrical components, or mechanical failures, require specialized tools and expertise to fix safely and effectively. Contact 1st Choice Mechanical’s team to learn why we’re the top HVAC contractor in the greater Phoenix area. Our team is prepared and available to assist you with a comprehensive range of HVAC services.