Outside Air Unit Not Turning On

Introduction

Your outside air unit, also known as the condenser, is a crucial part of your air conditioning system. It’s responsible for releasing heat from your home. When it’s not turning on, your house won’t cool down properly, especially during hot weather. This is a common problem that can be caused by several issues. It’s important to address this quickly to avoid discomfort and potential damage to your AC system. Don’t worry; you can often diagnose and fix the problem yourself before calling a technician.

Common Causes of outside air unit not turning on

Here are some of the most common reasons why your outside air unit might not be starting:

• Tripped Circuit Breaker: The breaker that powers your AC unit may have tripped due to an electrical overload.
• Thermostat Settings: The thermostat might not be set correctly to “Cool” or the temperature setting might be too high.
• Power Switch Off: There’s often a separate power switch near the unit; it may have been accidentally switched off.
• Dirty Condenser Coils: Dust, dirt, and debris can build up on the coils, preventing the unit from cooling properly and potentially causing it to shut down.
• Faulty Capacitor: The capacitor helps start and run the motor. If it’s weak or damaged, the unit won’t start.
• Frozen Evaporator Coil: If the inside evaporator coil is frozen, it can prevent the outside unit from turning on. This is often due to low refrigerant or restricted airflow.
• Contactor Problems: The contactor is an electrical switch that controls power to the unit. If it’s burnt or damaged, it won’t send power to the unit.
• Overheating: The unit might be overheating due to restricted airflow or other issues, causing a safety shut-off.
• Refrigerant Leak: Low refrigerant levels can cause the unit to shut down to prevent damage.

Symptoms Checklist

Use this checklist to help identify the issue more accurately:

• No cool air coming from the vents inside your house.
• The outside unit is completely silent (no humming or fan noise).
• You hear a clicking sound from the outside unit but nothing starts.
• The fan on the outside unit is not spinning.
• The inside blower fan is working, but the outside unit isn’t.
• The circuit breaker for the AC keeps tripping.

How to Fix outside air unit not turning on Step-by-Step Guide

Follow these steps to troubleshoot your outside air unit:

1. Check the Thermostat: Make sure the thermostat is set to “Cool” and the temperature is set lower than the current room temperature.
2. Check the Circuit Breaker: Go to your electrical panel and check the breaker for the AC unit. If it’s tripped (in the “off” position), flip it all the way to “off” and then back to “on.”
3. Check the Power Switch: Locate the power switch near the outside unit (it often looks like a light switch in a metal box) and make sure it’s in the “on” position.
4. Inspect the Condenser Coils: Look at the outside of the unit. Are the coils covered in dirt or debris? If so, proceed to step 5.
5. Clean the Condenser Coils: Turn off the power to the unit at the breaker. Use a garden hose (with a gentle spray nozzle) to carefully rinse the coils from the inside out. Avoid bending the fins. Let it dry completely before turning the power back on.
6. Check for Obstructions: Make sure there are no obstructions around the unit, such as plants, bushes, or debris, that could be blocking airflow. Allow at least 2-3 feet of clearance around the unit.
7. Check the Air Filter: A dirty air filter inside your house can restrict airflow and cause the evaporator coil to freeze. Replace the air filter if it’s dirty.
8. Wait and Restart: If you suspect overheating, turn off the unit and let it cool down for a few hours before turning it back on.
9. Listen for Sounds: When you turn the unit on, listen carefully. Do you hear a humming sound, a clicking sound, or nothing at all? This can give you clues about the problem.
10. Check the Contactor: (Caution: Disconnect Power First!) After turning off the breaker, you can visually inspect the contactor (usually behind an access panel). Look for signs of burning, pitting, or damage. If you see damage, this likely needs professional attention.
11. Inspect for Ice: Check the copper lines going into the inside unit (evaporator coil). Is there ice buildup? This indicates a frozen evaporator coil and can prevent the outside unit from running. Turn off the AC and let the ice thaw for several hours before restarting.
12. Ensure Proper Ventilation: Make sure that all vents inside your home are open and not blocked by furniture or other items. This will help ensure proper airflow and prevent the evaporator coil from freezing again.

Fix the Issue Without Buying Parts

Many issues can be resolved without spending money:

• Resetting: Simply turning the system off and on again (at the thermostat, breaker, and unit itself) can sometimes resolve minor glitches.
• Cleaning: Regular cleaning of the condenser coils and replacing air filters can prevent many problems.
• Visual Inspection: Careful inspection can reveal obvious issues like disconnected wires or obstructions.
• Proper Ventilation: Ensuring that vents are open and airflow is not restricted inside the house is essential.

When Replacement Might Be Necessary

Sometimes, repair isn’t enough. Consider replacement if:

• The unit is very old (15+ years) and inefficient.
• You’ve already tried multiple repairs, and the unit is still failing.
• The compressor (the heart of the unit) is failing.
• You have a refrigerant leak that is too expensive to repair.

Typical replacement costs can range from $3,000 to $7,000+ depending on the size and efficiency of the unit. Commonly failing parts include the compressor, capacitor, fan motor, and contactor. For more related activities, check out our Aircon Is Leaking Water.

Safety Warning

• Always disconnect power to the unit at the circuit breaker before attempting any repairs or cleaning.
• Never touch electrical components with wet hands or while standing on a wet surface.
• Be careful when using water to clean the coils. Avoid spraying water directly into electrical components.
• If you are not comfortable working with electricity, call a qualified HVAC technician.
• Refrigerant is harmful. Do not attempt to handle or repair refrigerant lines yourself.

Tools You May Need

• Screwdriver (Phillips and Flathead)
• Garden Hose with Spray Nozzle
• Work Gloves
• Flashlight
• Multimeter (Optional, for testing electrical components)

FAQ

Q: My unit is humming but not starting. What could be wrong?
A: This often indicates a problem with the capacitor or the compressor motor. It’s best to have a technician diagnose this.

Q: How often should I clean my condenser coils?
A: At least once a year, preferably in the spring before the cooling season begins.

Q: My breaker keeps tripping. Is it the AC unit?
A: It could be. Make sure nothing else is on the same circuit. If the breaker continues to trip, there may be an electrical fault in the unit that requires professional attention.

Q: What is the white PVC pipe coming from my inside unit?
A: This is a drain pipe for condensation. If it gets clogged, it can cause the unit to shut down. Check to make sure the drain is clear and that water can flow freely.

Conclusion

Troubleshooting an outside air unit that isn’t turning on can seem daunting, but many issues have simple solutions. By following these steps, you can often diagnose and fix the problem yourself, saving you time and money. If you’ve tried these steps and your unit is still not working, it’s best to call a qualified HVAC technician for further assistance. Don’t be afraid to try you might be surprised at what you can fix yourself!

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