Outside Unit Not Running When Ac Is On

Introduction

Is your air conditioner blowing warm air, even though the inside fan is running? The problem might be with your outside AC unit. When the outside unit isnt running while the inside unit is, your home won’t cool down. This is a common issue, especially during peak summer months, and addressing it quickly is important to prevent further damage to your system and ensure your comfort. Don’t delay a non-functional AC system can quickly become a costly problem and make your home unbearably hot.

Common Causes of outside unit not running when ac is on

Here are some common reasons why your outside AC unit might not be running:

No Power: The unit might not be receiving electricity due to a tripped breaker or blown fuse.
Thermostat Issues: The thermostat may not be properly set to “cool” or the temperature setting might be too high.
Capacitor Problems: The capacitor helps start and run the motor. If it’s faulty, the unit won’t start.
Dirty Condenser Coils: Dust, dirt, and debris can accumulate on the coils, preventing proper heat exchange and causing the unit to overheat and shut down.
Contactor Problems: The contactor is an electrical switch that sends power to the compressor and fan motor. If it’s damaged, it won’t allow power to flow.
Overload Protection: The unit might have an overload protection device that trips if the motor gets too hot.
Fan Motor Failure: The fan motor could be burned out or malfunctioning, preventing the fan from spinning and cooling the unit.
Compressor Failure: The compressor is the heart of the AC system. If it fails, the unit won’t cool.
Refrigerant Leaks: Low refrigerant levels can prevent the unit from running efficiently or at all.

Symptoms Checklist

Use this checklist to help diagnose the problem:

Inside fan is blowing air, but it’s not cold.
Outside unit is completely silent and the fan isn’t spinning.
You hear a humming sound from the outside unit, but the fan doesn’t start.
The circuit breaker for the AC unit has tripped.
The outside unit runs for a short time and then shuts off.
Ice buildup on the refrigerant lines near the outside unit.

How to Fix outside unit not running when ac is on Step-by-Step Guide

Follow these steps to troubleshoot your AC unit:

Check the Thermostat: Make sure the thermostat is set to “cool” and the temperature is set lower than the current room temperature.
Inspect the Breaker: Go to your electrical panel and check if the circuit breaker for the AC unit has tripped. If it has, reset it. If it trips again immediately, there may be a short circuit.
Examine the Disconnect Switch: Locate the disconnect switch near the outside unit and ensure it’s in the “on” position.
Visually Inspect the Unit: Look for any obvious signs of damage, such as loose wires, burnt components, or debris blocking the fan.
Clean the Condenser Coils: Use a garden hose (with a gentle spray nozzle) to rinse off any dirt, dust, or debris from the outside of the condenser coils. Be careful not to bend the fins.
Check the Capacitor: (CAUTION: Capacitors can store an electrical charge even when the power is off. It’s best to leave this step to a qualified technician if you’re not comfortable.) If you’re comfortable proceed with caution after disconnecting power to the unit. Visually inspect the capacitor (usually a cylindrical component). Look for bulging, leaking, or other signs of damage. A failing capacitor is a common cause of starting problems.
Check the Contactor: (CAUTION: Proceed with extreme caution and after disconnecting power.) The contactor should pull in when the thermostat calls for cooling. If it’s not pulling in, it may be faulty. Again, this step might be best left to a professional.
Inspect the Fan Motor: Check if the fan blades can spin freely. If they are stuck, there may be an obstruction or the motor may be seized.
Check for Ice Buildup: If there is ice on the refrigerant lines, the unit may be low on refrigerant or have airflow problems. Turn off the unit and allow the ice to melt completely. Then, try running it again.
Check the Air Filter: A dirty air filter restricts airflow and can cause the system to overheat. Replace the air filter if it’s dirty. (Although it mostly affects the indoor unit.)
Wait and Restart: Sometimes, the unit’s overload protection can trip. Turn off the unit for 30 minutes and then try turning it back on.

Fix the Issue Without Buying Parts

Here are some things you can try before considering replacement parts:

Resetting the Breaker: Sometimes a simple reset is all it takes.
Thorough Cleaning: Clean the condenser coils, remove debris, and ensure good airflow.
Thermostat Recalibration: Ensure your thermostat is functioning correctly and properly calibrated.
Visual Inspection: Regularly check for loose wires, leaks, or other obvious issues.
Basic Maintenance: Change air filters regularly and keep the area around the outside unit clear.

When Replacement Might Be Necessary

If you’ve tried all the troubleshooting steps and the unit still isn’t working, it might be time to consider replacing parts or the entire unit. Common parts that fail include:

Capacitor: $20 – $100 (but can be dangerous to replace yourself)
Fan Motor: $100 – $300
Contactor: $30 – $150
Compressor: (Very expensive, often justifies replacing the entire unit)

A full AC unit replacement can range from $3,000 to $7,000, depending on the size and efficiency of the new unit.

Safety Warning

Always turn off the power to the AC unit at the breaker before performing any maintenance.
Be careful when working around electrical components. If you’re not comfortable, hire a qualified electrician.
Avoid working on the AC unit in wet conditions.
Capacitors can store an electrical charge even when the power is off. Discharge the capacitor before handling it or leave it to professional.

Tools You May Need

Screwdrivers (various sizes)
Wrench set
Multimeter (for electrical testing use with caution!)
Garden hose with a spray nozzle
Fin comb (for straightening bent condenser fins)
Work gloves

FAQ

Here are some frequently asked questions:

Q: Why is my AC unit humming but not starting? A: This could be a sign of a failing capacitor or a seized motor.
Q: How often should I clean my condenser coils? A: At least once a year, or more often if you live in a dusty area.
Q: My AC unit is freezing up. What should I do? A: Turn off the unit and allow the ice to melt. Check the air filter and ensure there’s adequate airflow. If the problem persists, you may have a refrigerant leak.
Q: How do I know if my refrigerant is low? A: Signs of low refrigerant include weak airflow, ice buildup on the refrigerant lines, and warm air blowing from the vents.

Conclusion

Troubleshooting your AC unit can seem daunting, but by following these steps, you can often diagnose and fix the problem yourself. Remember to prioritize safety and consult a qualified technician if you’re uncomfortable with any of the steps. Often, a simple cleaning or reset is all it takes to get your AC unit running smoothly again. But if DIY isn’t your cup of tea, don’t hesitate to call a professional to handle the job.