When you find that your indoor AC unit is working but the outdoor unit isn't, it can be a significant concern, especially during extreme weather conditions. This scenario usually suggests an underlying issue that needs prompt attention.
Initial Troubleshooting Steps
Before you call a professional, there are a few basic troubleshooting steps you can try:
Check the On-Off Switch
First, ensure the outdoor unit's on-off switch near the unit itself is in the "on" position. It may have been accidentally switched off.

Inspect the Circuit Breaker
Verify the circuit breaker in your electrical panel hasn't tripped. If it has, switching it back on may resolve the issue temporarily, but frequent trips could indicate a serious problem that needs professional attention.
Thermostat Settings
Make sure your thermostat is set to "cool" and the temperature is set lower than the current room temperature. Incorrect thermostat settings can disrupt the communication between the indoor and outdoor units.
Potential Mechanical Issues
If basic troubleshooting doesn't solve the problem, there could be mechanical issues at play:

Capacitor and Contactor Failure
Failures in these components can prevent the outdoor unit from functioning. Signs include humming noises, intermittent starting and stopping, and frequent circuit breaker trips.
Refrigerant Levels
Low refrigerant levels can cause the outdoor unit to shut down. This issue requires a professional to diagnose the problem, fix leaks if necessary, and replenish the refrigerant.
Power Supply Issues
Another common cause could be power-related:
Disconnect Switch
Check the disconnect switch near the outdoor unit. If it has flipped, resetting it might solve the problem.

Wiring Problems
Inspect the wiring for any visible signs of damage. Electrical issues are hazardous and should be handled by a certified electrician.
When to Call a Professional
Some issues require the expertise of a professional HVAC technician. If refrigerant levels are low, mechanical components have failed, or you suspect an electrical problem, it's best to seek professional help to avoid further complications and ensure safety.
Importance of Regular Maintenance
Regular maintenance is crucial to keep your AC system running efficiently. Annual inspections help identify potential issues before they turn into costly repairs. By maintaining your unit, you can ensure it operates safely and effectively.
For residents in Central New Jersey, Skylands Energy Service offers HVAC maintenance, installations, replacements, and repairs to keep your systems in top condition.
