If your split AC compressor is not working but the fan is running, you’re likely dealing with a common issue that can have multiple causes. Before calling an HVAC technician, follow this step-by-step troubleshooting guide to diagnose and fix the problem yourself.
Why Is My Split AC Compressor Not Working But Fan Is Running?
If the fan kicks on but the compressor is not working, it usually indicates a problem in the electrical or refrigeration system. Some of the most common causes include:
- Faulty capacitor preventing the compressor from starting
- Low refrigerant levels triggering a safety switch that shuts off the compressor
- Bad compressor due to mechanical failure or burnout
- Electrical issues such as bad wiring, relay failure, or a tripped circuit breaker
- Clogged air filters or condenser coils leading to overheating and safety shutdowns
Now, let’s go through a step-by-step process to identify and fix the issue.
Step-by-Step Troubleshooting Guide
Step 1: Check the AC Capacitor
A bad capacitor is one of the most common reasons why the condenser fan is running but the compressor is not. The capacitor stores and delivers an electrical charge that helps start the compressor.
How to check the capacitor:
- Turn off the AC unit’s power at the breaker.
- Locate the capacitor inside the outdoor unit.
- Look for bulging, leaks, or burn marks.
- Use a multimeter to test capacitance (it should match the rating on the capacitor).
- If the capacitor is faulty, replace it.
If the HERM side of the dual-run capacitor fails, the fan will still run, but the compressor won’t start.
Step 2: Inspect Refrigerant Levels
If your split AC is not cooling but the fan is running, the system might have low refrigerant. Many AC units have a low-pressure safety switch that shuts off the compressor when refrigerant is low but allows the fan to keep running.
Solution:
- If your AC is blowing warm air and the compressor won’t start, call a professional to check refrigerant levels.
- If refrigerant is low, it might indicate a leak that needs to be repaired before recharging the system.
Step 3: Check for Electrical Issues
If your AC compressor is not turning on, electrical problems could be the cause.
How to check for electrical problems:
- Ensure the circuit breaker is not tripped.
- Inspect wiring connections at the capacitor and contactor.
- Test the contactor relay for proper function.
- Use a multimeter to confirm voltage at the compressor terminals.
If there is no power reaching the compressor, you may have a bad contactor or a wiring issue.
Step 4: Test the Compressor
If the air conditioner compressor is not turning on, the compressor itself may be faulty. A common issue in inverter mini-split AC units is when the fan operates but the compressor does not start due to electrical or internal failures.
How to check the compressor:
- Turn off power to the AC unit.
- Use a multimeter to check resistance between the compressor terminals (Common, Run, and Start).
- If the readings are unstable or show an open circuit (OL), the compressor is likely defective.
- Check for loose or burnt wiring connections at the compressor.
Watch this troubleshooting video for more details:
Fan Works/Starts But Compressor Fails In Inverter Mini Split AC
Step 5: Check for Overheating or Blockages
If your AC fan is running but the compressor is not, the compressor may have overheated and shut off.
How to fix overheating or blockages:
- Clean dirty condenser coils to improve airflow.
- Replace clogged air filters.
- Ensure proper ventilation around the outdoor unit.
An overheated compressor may shut off temporarily and restart once it cools down.
Step 6: Verify the Thermostat Settings
Incorrect thermostat settings can also cause an issue where the compressor is not turning on, but the fan is running.
Fix:
- Lower the temperature setting on the thermostat.
- Make sure it’s set to cooling mode.
- Replace thermostat batteries if necessary.
If the thermostat is not signaling the compressor to turn on, recalibrating or replacing it may be required.
Quick Troubleshooting Reference Table
| Problem | Possible Cause | Solution |
| Fan is running but compressor is not | Bad capacitor | Replace capacitor |
| Compressor tries to start but shuts off | Overheating | Clean coils, check airflow |
| Compressor is completely silent | Electrical issue | Check wiring, contactor, and fuses |
| AC is running but not cooling | Low refrigerant | Call technician for a recharge |
Frequently Asked Questions
Can a bad capacitor cause my AC compressor to stop working but let the fan run?
Yes. The HERM (compressor) side of a dual-run capacitor can fail while the fan side remains operational.
Why is my AC compressor not turning on but the fan is blowing?
The most common causes include a bad capacitor, low refrigerant, electrical failure, or a faulty compressor.
How do I reset my AC compressor?
- Turn off the AC unit at the thermostat and breaker.
- Locate the reset button on the outdoor unit (if available).
- Press and hold the reset button for 3-5 seconds.
- Restore power and restart the AC system.
What happens if the AC compressor fails?
If the compressor fails, the AC will not cool properly. You may notice short cycling, loud noises, or breaker trips.
Final Thoughts: Fixing a Split AC Compressor That’s Not Working
If your split AC compressor is not working but the fan is running, the most likely causes are:
- Faulty capacitor (replace it first)
- Low refrigerant (requires professional service)
- Electrical issues (check wiring, relay, and contactor)
- Overheating or blockages (clean coils, filters, and ensure proper airflow)
- Compressor failure (may need replacement)
If your compressor still won’t start after troubleshooting, it’s time to consult a certified HVAC professional. Home Revista connects homeowners with vetted experts, leveraging data-driven insights and high-quality first-party leads to ensure reliable, efficient service tailored to your needs.
