When an AC unit won't turn on, and you've already confirmed that the fuses and breakers are working fine, there are several steps you can take to troubleshoot and determine if the problem lies with the compressor or the thermostat. Here's a step-by-step guide to help you diagnose the issue:
Check the thermostat settings: Ensure that the thermostat is set to the cooling mode and that the temperature is set lower than the current room temperature. Sometimes, the issue might be as simple as incorrect thermostat settings.
Test the thermostat: Turn off the power to the AC unit and carefully remove the thermostat cover. Check for loose or disconnected wires. If everything seems fine, you can try bypassing the thermostat temporarily to see if the AC turns on. To do this, you can carefully disconnect the wires connected to the thermostat and then connect the R (power) and Y (cooling) wires together. If the AC turns on after bypassing the thermostat, it indicates a faulty thermostat as the culprit.
Inspect the capacitor: The capacitor is a critical component that helps start the compressor and the fan motor. If the capacitor is faulty, it could prevent the compressor from starting. You'll need a multimeter to test the capacitor's capacitance. If you're not familiar with this process, it's best to have a professional HVAC technician perform the test and replace the capacitor if needed.
Listen for unusual sounds: When you try to turn on the AC, listen for any clicking sounds or humming noises coming from the compressor. If you hear clicking sounds, it could be an indication of a faulty start capacitor. If there's a humming noise but the compressor doesn't start, it may indicate a locked-up compressor or a compressor issue.
Check the power supply to the compressor: If you have the necessary skills and tools, you can use a multimeter to check if power is reaching the compressor. If there's no power reaching the compressor, it could be due to a wiring issue, a faulty contactor, or a problem with the control board.
Consult a professional: If you've tried the above steps and are still unsure about the root cause of the problem, it's best to call a licensed HVAC technician. They have the expertise and tools to diagnose the issue accurately and safely. Working with electrical components can be dangerous, so it's essential to prioritize safety and leave complex repairs to professionals.
In summary, troubleshooting an AC unit that won't turn on involves a series of checks to narrow down the problem. You can start by examining the thermostat, checking the capacitor, listening for unusual sounds, and testing the power supply to the compressor. If you're not confident in performing these checks, it's best to seek professional help to avoid potential hazards and further damage to your AC unit.