Heat Is On But Outside Unit Not Running

Introduction

Discovering that your heat is on inside, but the outside unit isn’t running can be a frustrating and concerning situation, especially during cold weather. This usually indicates a problem within your heating system that needs to be addressed promptly. Ignoring this issue can lead to a cold house and potentially higher energy bills as your backup heating system struggles to keep up. This guide will help you understand common causes and walk you through some troubleshooting steps you can take before calling a professional.

Common Causes of Heat is On But Outside Unit Not Running

Here are some potential reasons why your outside unit might not be running, even though your thermostat is set to heat:

Thermostat Settings: The thermostat might not be properly set to “Heat” or the desired temperature is not high enough to trigger the outside unit.
Dirty Air Filter: A clogged air filter restricts airflow, causing the system to overheat and potentially shut down the outside unit as a safety measure.
Frozen Coils: Ice buildup on the outside unit’s coils can prevent it from running. This is more common in colder climates.
Defrost Cycle: The outside unit may be in its defrost cycle, which temporarily shuts down the compressor to melt any ice that has formed.
Capacitor Problems: The capacitor is responsible for starting the motor in the outside unit. A failing capacitor can prevent the unit from starting.
Contactor Problems: A contactor is an electrical switch that allows power to flow to the outdoor unit. A bad contactor can prevent the unit from starting.
Overload Protection: The outside unit has overload protection that shuts it down if it gets too hot or if there is an electrical problem.
Refrigerant Leaks: Low refrigerant levels can prevent the outside unit from running efficiently, or at all.
Compressor Failure: The compressor is the heart of the outside unit. A failing compressor will stop the unit from working.
Breaker Issues: A tripped breaker can cut power to the outside unit.

Symptoms Checklist

Use this checklist to help diagnose the problem:

Is the thermostat set to “Heat” and at a temperature higher than the current room temperature?
Is the air filter clean or dirty?
Is there ice buildup on the outside unit’s coils?
Is the fan in the outside unit spinning at all?
Are you hearing any unusual noises from the outside unit?
Is the breaker for the outside unit tripped?
Is the indoor blower fan working?
Is warm air coming from the vents? (Even if it’s just slightly warm).

How to Fix Heat is On But Outside Unit Not Running Step-by-Step Guide

Check the Thermostat: Ensure the thermostat is set to “Heat” mode and the temperature is set a few degrees higher than the current room temperature.
Inspect the Air Filter: Remove the air filter and check if it’s dirty. If it is, replace it with a new one.
Check the Breaker: Go to your electrical panel and check if the breaker for the outside unit has tripped. If it has, reset it. If it trips again immediately, there may be a more serious electrical issue.
Look for Ice Buildup: Inspect the outside unit for ice buildup on the coils. If you see ice, try running the system in “Emergency Heat” mode (if available) to help defrost it. Monitor the unit closely.
Inspect the Disconnect Switch: There’s typically a disconnect switch near the outdoor unit. Ensure it is in the “On” position.
Listen to the Unit: Try to hear if the outdoor unit is humming or making any noise that could be a sign of it trying to start. If there is a humming sound and fan isn’t starting, it can be a sign that the capacitor is failing.
Check for Obstructions: Make sure that the outdoor unit isn’t blocked by debris, snow, or plants that could be restricting airflow.
Wait and Observe: If the unit has recently gone through a defrost cycle, wait 30-60 minutes to see if it starts up on its own.
Check the Contactor: Warning: This involves working with electricity! If you’re not comfortable, skip this step and call a professional. With the power OFF at the breaker, carefully inspect the contactor (a switch inside the outdoor unit). Look for signs of burning or damage.
Clean the Outdoor Unit: Turn off the power at the breaker and use a garden hose to gently rinse away any dirt or debris from the outside of the unit. Avoid spraying water directly into the electrical components.
Emergency Heat Mode: If available, engage the “Emergency Heat” setting. This will use the electric resistance heating elements in your indoor unit to heat your home. This is a temporary solution while you troubleshoot the main issue.

Fix the Issue Without Buying Parts

Often, you can resolve the issue without immediately buying new parts:

Resetting the System: Turn off the thermostat and the breaker for the outside unit. Wait a few minutes, then turn them back on. This can sometimes reset the system and resolve minor glitches.
Cleaning the Coils: Periodically clean the outside unit’s coils with a fin comb or a soft brush to remove dirt and debris that can restrict airflow.
Thermostat Recalibration: Check your thermostat’s manual for instructions on how to recalibrate it. This can ensure accurate temperature readings and proper operation.
Regular Inspection: Regularly inspect the outside unit for any signs of damage, debris, or ice buildup. Addressing these issues early can prevent more serious problems.
Proper Landscaping: Keep bushes, shrubs, and other vegetation trimmed away from the outside unit to ensure proper airflow.

When Replacement Might Be Necessary

While it’s best to try troubleshooting and repair first, sometimes replacement is necessary. Here are some situations where that might be the case:

Compressor Failure: Replacing a compressor can be expensive, often ranging from $800 to $2,500. If the compressor has failed, it might be more cost-effective to replace the entire unit.
Refrigerant Leaks: Locating and repairing refrigerant leaks can be costly, and if the leaks are extensive or in hard-to-reach areas, replacement might be the best option.
Major Component Failure: If multiple major components, such as the compressor, fan motor, and control board, are failing, it might be more economical to replace the entire unit rather than repairing individual parts.
Age of the Unit: If your unit is over 15 years old, it may be nearing the end of its lifespan, and replacement might be a more prudent investment than costly repairs.

Commonly failing parts include: capacitors ($50-$200), contactors ($30-$100), and fan motors ($150-$500).

Safety Warning

Always turn off the power to the outside unit at the breaker before attempting any repairs or cleaning.
Avoid working on the system in wet conditions.
If you’re not comfortable working with electricity, call a qualified HVAC technician.
Be careful when handling sharp objects or tools.
Refrigerant is harmful if inhaled. Avoid contact with refrigerant.

Tools You May Need

Screwdrivers (Phillips and flathead)
Wrench set
Multimeter (for testing electrical components use with extreme caution!)
Fin comb (for cleaning coils)
Garden hose
Work gloves

FAQ

Q: Why is my outside unit not running but the inside fan is blowing cold air?
A: This likely indicates a problem with the outside unit, such as a frozen coil, a faulty capacitor, or a tripped breaker.
Q: How long should the defrost cycle last?
A: The defrost cycle typically lasts between 5 and 15 minutes.
Q: Can I add refrigerant to my system myself?
A: No. Refrigerant handling requires specialized equipment and certifications. It’s best to call a qualified HVAC technician.
Q: My outside unit is making a loud buzzing noise. What could that be?
A: A loud buzzing noise could indicate a problem with the compressor, capacitor, or contactor. Turn off the unit and call a technician.
Q: How often should I change my air filter?
A: It depends on the type of filter and the air quality in your home. Generally, you should change it every 1-3 months.
Q: Can a dirty air filter cause the outside unit to stop working?
A: Yes, a dirty air filter can restrict airflow, causing the system to overheat and potentially shut down the outside unit.

Conclusion

Troubleshooting a non-operational outside unit while your heat is on inside can be challenging, but by following these steps, you can often identify and resolve the problem yourself. Remember to prioritize safety and call a qualified HVAC technician if you’re not comfortable working with electricity or refrigerant. Don’t hesitate to give these troubleshooting steps a try – you might be able to save yourself a service call! However, if the problem persists or is beyond your comfort level, it’s always best to consult with a professional.