Central Air Conditioner Compressor Not Turning On

Introduction

If your central air conditioner is blowing warm air, the problem might be that the compressor isn’t turning on. The compressor is the heart of your AC system, responsible for circulating refrigerant, which cools the air. When it fails to start, your AC simply won’t cool. This usually happens on hot days when your AC is working its hardest, making it a very uncomfortable and urgent problem to fix. Ignoring this issue can lead to further damage to your system and more expensive repairs down the road. Let’s troubleshoot some potential causes.

Common Causes of Central Air Conditioner Compressor Not Turning On

Here are several reasons why your AC compressor might not be starting:

• Tripped Circuit Breaker: The breaker that powers your AC unit may have tripped due to an overload.
• Faulty Capacitor: The capacitor helps start and run the compressor motor. If it’s weak or damaged, the compressor won’t turn on.
• Dirty Condenser Coils: Dirt and debris on the outdoor condenser coils can restrict airflow, causing the compressor to overheat and shut down.
• Refrigerant Leak: Low refrigerant levels can prevent the compressor from starting as a safety measure.
• Failed Contactor: The contactor is an electrical switch that sends power to the compressor. A faulty contactor won’t allow the compressor to receive power.
• Overheating: The compressor might have overheated, triggering an internal overload protector.
• Frozen Evaporator Coil: A frozen evaporator coil (indoor unit) restricts airflow, which can indirectly cause the compressor to shut down.
• Wiring Problems: Loose or corroded wiring connections can interrupt the power supply to the compressor.
• Bad Compressor Motor: The compressor motor itself could be damaged or worn out.

Symptoms Checklist

Use this checklist to help pinpoint the problem:

• Warm air blowing from vents.
• The outdoor AC unit is completely silent (no fan or compressor sound).
• You hear a humming sound coming from the outdoor unit, but the compressor doesn’t start.
• The circuit breaker for the AC unit trips frequently.
• The fan on the outdoor unit is running, but the air isn’t cooling.
• Ice buildup on the refrigerant lines of the outdoor or indoor unit.

How to Fix Central Air Conditioner Compressor Not Turning On Step-by-Step Guide

Follow these steps to troubleshoot your AC compressor:

1. Check the Thermostat: Make sure your thermostat is set to “Cool” and the temperature is set lower than the current room temperature. Also, check the batteries if your thermostat has them.
2. Inspect the Circuit Breaker: Locate the circuit breaker for your AC unit in your electrical panel. If it’s tripped (in the “off” or middle position), flip it all the way “off” and then back “on”.
3. Examine the Outdoor Unit: Visually inspect the outdoor unit for any obvious signs of damage, such as bent fins, loose wires, or debris.
4. Clean the Condenser Coils: Turn off the power to the AC unit at the breaker. Use a garden hose (with a gentle spray nozzle) to clean the outdoor condenser coils. Spray from the inside out to remove dirt and debris.
5. Check the Contactor: Locate the contactor inside the outdoor unit’s control panel. It’s a small electrical switch with wires connected to it. Use a non-conductive object (like a plastic pen) to gently push the contactor in. If the compressor starts when you do this, the contactor is likely faulty and needs replacement (by a professional). Note: Be extremely careful when working near electrical components.
6. Inspect the Capacitor: Locate the capacitor (usually a cylindrical metal component) near the contactor. Look for signs of bulging, leaking, or corrosion. A bad capacitor can prevent the compressor from starting. Note: Capacitors can hold an electrical charge even when the power is off. It’s best to have a professional handle capacitor testing and replacement.
7. Check for Ice Buildup: Inspect the indoor evaporator coil (usually inside the air handler) and the refrigerant lines for ice buildup. If you see ice, turn off the AC and allow it to thaw completely (several hours or overnight) before restarting.
8. Check the Air Filter: A clogged air filter restricts airflow and can cause the evaporator coil to freeze. Replace the air filter with a clean one.
9. Reset the Compressor Overload Protector: Some compressors have an internal overload protector that can trip if the compressor overheats. To reset it, turn off the power to the AC unit at the breaker for at least 30 minutes, then turn it back on.
10. Listen for Sounds: When the AC is supposed to be running, listen closely to the outdoor unit. A humming sound might indicate that the compressor is trying to start but failing, which could point to a capacitor or motor problem.
11. Check Wiring Connections: Turn off the power to the AC unit. Visually inspect the wiring connections inside the outdoor unit’s control panel for any loose or corroded wires. Tighten any loose connections.

Fix the Issue Without Buying Parts

Many issues can be resolved without immediately buying parts:

• Resetting the Breaker: Simply resetting a tripped breaker can often solve the problem.
• Cleaning the Coils: Regularly cleaning the condenser coils improves airflow and prevents overheating.
• Replacing Air Filter: Replacing a dirty air filter ensures proper airflow and prevents the evaporator coil from freezing.
• Thawing Ice Buildup: Letting the system thaw out completely clears any blockages from frozen coils.
• Visual Inspection: Thoroughly checking for loose wires or debris can save you from unnecessary repairs.

When Replacement Might Be Necessary

If the compressor motor is damaged, or if the contactor or capacitor are visibly damaged and testing indicates failure, they will likely need replacement. Replacing a compressor can cost between $800 and $2500, including labor. A contactor usually costs between $50 and $200, and a capacitor typically ranges from $20 to $100. Compressor, contactor, and capacitor are the most commonly replaced parts in this type of failure. If these steps haven’t solved the problem, consider calling a qualified HVAC technician. For more related activities, check out our 2012 Camaro Ac Blowing Hot Air.

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 while standing on a wet floor.
• Be careful when handling capacitors, as they can store an electrical charge. It’s best to have a professional handle capacitor testing and replacement.
• If you’re not comfortable working with electricity, call a qualified HVAC technician.

Tools You May Need

• Screwdrivers (Phillips and flathead)
• Wrench set
• Garden hose with spray nozzle
• Multimeter (for testing electrical components – optional, and requires knowledge of electrical testing)
• Non-conductive object (like a plastic pen)

FAQ

Here are some frequently asked questions about AC compressor problems:

• Q: My AC compressor hums but doesn’t start. What could be the problem?
  A: A humming sound often indicates a faulty capacitor or a problem with the compressor motor itself.
• Q: How do I know if my capacitor is bad?
  A: Look for signs of bulging, leaking, or corrosion. Also, a bad capacitor often prevents the compressor from starting.
• Q: Why does my AC breaker keep tripping?
  A: This could be due to an overloaded circuit, a faulty compressor, or a problem with the wiring.
• Q: Can I replace the compressor myself?
  A: Replacing a compressor is a complex and potentially dangerous task that should be performed by a qualified HVAC technician. It involves handling refrigerant and working with electrical components.

Conclusion

Troubleshooting a central AC compressor that won’t turn on can seem daunting, but by following these steps, you can often identify and resolve the issue. Remember to prioritize safety and take your time. If you’re not comfortable working with electricity or refrigerant, don’t hesitate to call a qualified HVAC technician for assistance. With a little effort, you can often get your AC back up and running, keeping your home cool and comfortable.

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