Outside Ac Unit Will Not Come On

Introduction

Having your outside AC unit refuse to start, especially on a hot day, is a frustrating experience. It’s more than just an inconvenience; it can quickly make your home uncomfortable and even pose a health risk to vulnerable individuals like children or the elderly. The most common scenarios include a sudden failure during peak usage hours or after a period of inactivity, such as at the start of the cooling season. Addressing this issue promptly is important to prevent further damage to your system and restore comfort to your home.

Common Causes of Outside AC Unit Will Not Come On

Here are some of the common reasons why your outside AC unit might be failing to start:

• Tripped Circuit Breaker: The circuit breaker dedicated to your AC unit may have tripped due to an overload.
• Faulty Capacitor: The capacitor provides the initial jolt of energy to start the motor. If it’s weak or dead, the unit won’t start.
• Dirty Condenser Coils: Accumulated dirt and debris can restrict airflow and cause the unit to overheat and shut down.
• Frozen Evaporator Coils: Restricted airflow inside the house can cause the indoor coils to freeze, which then shuts down the entire system.
• Loose Wiring: Loose or corroded electrical connections can prevent the unit from receiving power.
• Defective Contactor: The contactor is an electrical switch that allows power to flow to the compressor and fan motor. A faulty contactor can prevent the unit from starting.
• Thermostat Issues: A malfunctioning or incorrectly set thermostat might not be signaling the AC unit to turn on.
• Overload Protection: The compressor has a built-in overload protector that shuts it down if it gets too hot.

Symptoms Checklist

Use this checklist to accurately identify the problem:

• The inside fan is blowing, but the air is not cold.
• The outside unit is completely silent and shows no sign of life.
• You hear a humming sound from the outside unit, but the fan isn’t spinning.
• The circuit breaker for the AC keeps tripping.
• The thermostat is set to “cool,” but nothing is happening.
• Ice is visible on the copper lines of the outdoor unit.

How to Fix Outside AC Unit Will Not Come On Step-by-Step Guide

1. Check the Thermostat: Ensure the thermostat is set to “cool” and the temperature is set lower than the current room temperature. Make sure the thermostat has fresh batteries.
2. Inspect the Circuit Breaker: Locate the circuit breaker for your AC unit in your electrical panel. If it’s tripped (usually in the middle position), switch it all the way off and then back on.
3. Power Cycle the AC: Turn off the AC at the breaker. Wait 30 minutes and then turn it back on. This can sometimes reset the system.
4. Inspect the Disconnect Switch: Near your outside unit, there’s usually a disconnect switch (a small box with a handle). Make sure it’s in the “on” position.
5. Clean the Condenser Coils: Use a garden hose (with a gentle spray nozzle) to wash away dirt and debris from the outside of the condenser coils. Be careful not to bend the fins.
6. Check for Obstructions: Ensure there are no bushes, weeds, or other obstructions blocking airflow around the outside unit.
7. Inspect the Fan Blades: Make sure the fan blades are free from debris and can spin easily. If they’re stuck, try carefully removing any obstructions.
8. Check the Air Filter: A dirty air filter restricts airflow to the indoor unit, potentially causing the evaporator coils to freeze. Replace the air filter if it’s dirty.
9. Look for Ice on the Copper Lines: If you see ice on the copper lines going into the outdoor unit, it could indicate frozen evaporator coils. Turn off the AC and allow the ice to thaw completely (this could take several hours).
10. Listen for Unusual Noises: Pay attention to any humming, buzzing, or clicking sounds coming from the outside unit. These could indicate a problem with the capacitor or compressor.
11. Inspect Wiring Connections (If Comfortable): CAUTION: Turn off the power at the breaker before inspecting wiring! Visually inspect the wiring connections inside the unit for looseness or corrosion. If you see any, carefully tighten them with a screwdriver. If you’re not comfortable working with electricity, skip this step.

Fix the Issue Without Buying Parts

Often, a simple reset, cleaning, or visual inspection can resolve the problem without needing to buy replacement parts:. For more related activities, check out our My Aircon Suddenly Stopped Working.

• Reset the System: As mentioned earlier, turning off the AC at the breaker for 30 minutes can reset the system.
• Regular Cleaning: Cleaning the condenser coils and replacing the air filter regularly (every 1-3 months) can prevent many problems.
• Visual Inspections: Periodically check for obstructions, loose wiring, and signs of ice buildup.

When Replacement Might Be Necessary

If you’ve tried all the troubleshooting steps above and your AC unit still isn’t working, a replacement part may be necessary. The most common parts to fail are the capacitor ($20-$100), contactor ($30-$150), or, in the worst-case scenario, the compressor ($500-$2000 including labor). If the compressor is the problem, consider replacing the entire unit. A new AC unit installation generally ranges from $3,000 to $8,000, depending on the size and efficiency of the unit.

Safety Warning

• Always turn off the power to the AC unit at the circuit breaker before performing any maintenance or repairs.
• Avoid working on electrical components if you are not comfortable or experienced. Call a qualified technician.
• Do not spray water directly into the electrical components of the AC unit.
• Be careful when handling sharp objects or tools.
• If you suspect a refrigerant leak, do not attempt to repair it yourself. Contact a qualified HVAC technician.

Tools You May Need

• Screwdriver (Phillips and flathead)
• Wrench
• Garden hose with spray nozzle
• Multimeter (for testing electrical components, optional)
• Air filter

FAQ

Here are some frequently asked questions:

• Q: Why does my AC unit keep tripping the circuit breaker? A: This could be due to an overloaded circuit, a faulty capacitor, or a failing compressor.
• Q: How often should I clean my AC condenser coils? A: At least once a year, preferably before the start of the cooling season. If you live in a dusty area, you may need to clean them more frequently.
• Q: What does a bad capacitor sound like? A: A bad capacitor may produce a humming or buzzing sound. The fan motor may also struggle to start.
• Q: Can I replace the capacitor myself? A: Yes, but only if you are comfortable working with electricity and know how to safely discharge a capacitor. Otherwise, call a qualified technician.

Conclusion

Troubleshooting a non-functioning outside AC unit can seem daunting, but by following these steps, you can often identify and resolve the issue yourself. Remember to prioritize safety and consult with a qualified HVAC technician if you’re uncomfortable with any of the procedures or if the problem persists. With a little effort, you can get your AC back up and running and restore comfort to your home!

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