Red And Green Light Blinking On AC Unit: Causes, Troubleshooting, And Solutions For American Homes

Flashing red and green lights on an air conditioning unit often signal a malfunction or system alert. These indicators warn homeowners of issues such as electrical faults, sensor errors, or required maintenance. Understanding what red and green blinking lights mean on an AC unit helps users quickly resolve problems and prevent costly breakdowns. This guide details possible causes, step-by-step troubleshooting, and when to call a professional for different brands commonly found in American residences.

Common Causes Of Red And Green Light Blinking On Air Conditioners

AC units use indicator lights to provide instant feedback about their operational status. Blinking red and green lights often denote one of the following issues:

• Electrical problems: Power fluctuations or internal wiring faults.
• Thermistor or sensor malfunctions: Temperature sensors might have failed or disconnected.
• Refrigerant leaks or pressure issues: Low or high pressure triggers alerts for safety.
• Filter, coil, or airflow blockages: Dirt and debris restrict proper function.
• Communication errors: Miscommunication between indoor and outdoor boards.
• System overload or protection mode: Protection circuits intervene during abnormal load.

Identifying the cause based on the blink pattern and unit model is crucial for proper troubleshooting.

What Do Red And Green Light Blinking Patterns Mean?

The meaning of blinking lights can vary by manufacturer and model. Each pattern—whether alternating, simultaneous, or specific sequences—serves as an error code that directs the user to the source of the problem.

Brand	Red Light Blinking	Green Light Blinking	Both Lights Blinking
LG	Indoor unit failure	Outdoor communication error	Sensor or main board fault
Daikin	Thermistor error	Compressor or overcurrent	Refrigerant leak or protection mode
Mitsubishi	Filter alert or reset needed	Operation timer	Communication error
Carrier	Safety switch triggered	High-pressure fault	Logic board error

Check your owner’s manual for model-specific light patterns and error references.

Troubleshooting Steps For Blinking Red And Green Lights

Initial Safety Measures

• Turn off the AC unit to prevent electrical hazards.
• Disconnect the unit from the power source.
• Wait a few minutes before attempting any checks.

Never attempt advanced repairs unless you have proper expertise; electrical components carry shock risks.

Check Power Supply And Reset

• Confirm stable power supply: Inspect circuit breakers, fuses, and outlets.
• Reset the AC unit by turning it off for 5 minutes, then back on.

If lights continue flashing, further investigation is necessary.

Examine Filters And Airflow

• Clean or replace filters: Clogged filters trigger error codes and hamper airflow.
• Check vents and coils for visible dirt or blockages.

Maintaining clear airflow often stops error lights from blinking.

Inspect Sensors And Thermostats

• Ensure sensors are connected securely.
• Look for signs of wear or corrosion on sensor wiring.

Sensor issues directly cause blinking patterns, especially in newer ductless systems.

Test Indoor And Outdoor Communication

• Check wiring connections between indoor and outdoor units.
• Listen for unusual sounds from the outdoor compressor.

Many multi-split and mini-split systems rely on solid communication loops to avoid faults.

Brand-Specific Red And Green Blinking Solutions

LG AC Units

LG air conditioners frequently use red and green lights for error signaling. Common reasons for blinking include:

• Indoor blower motor failure.
• Outdoor unit protection mode.
• Communication loss between units.

Steps to fix:

• Reset the power and clear any blockages.
• Press the “Reset” or “Filter” button if available.
• If unresolved, consult a certified LG technician.

Daikin AC Units

Red and green blinking lights in Daikin ACs signal refrigerant cycle faults or thermistor problems.

• Inspect and clean air filters.
• Ensure the remote control batteries are functional.
• If the pattern persists, check for frozen coils or call service for possible sensor replacement.

Mitsubishi Electric AC Units

Mitsubishi units frequently use green blinking for filter cleaning reminders. Red lights usually indicate protection mode or circuit errors.

• Reset filter alarm by holding the reset button for several seconds.
• Test operation after clearing any blockages.
• Contact Mitsubishi support for error code decoding if both lights blink in a repeating pattern.

Other Brands: Carrier, Trane, Goodman, And More

American central AC brands follow similar logic. Simultaneous red and green blinks often mean:

• Thermostat or control board issues
• Relay faults or compressor lockout
• Emergency switch activation

Check for recent power outages or tripped safety switches. Reset the system and note any error codes flashing on the control panel.

When To Call A Professional Technician

Some scenarios demand immediate expert intervention:

• Persistent blinking after reset
• Burning smells or smoke from the unit
• Loud electrical noises or sparks
• Leaking refrigerant or water under the unit
• Repeated circuit breaker trips

Attempting DIY repairs with these symptoms can void warranties or further damage components.

Preventing Future Blinking Light Issues On AC Units

Consistent maintenance dramatically lowers the risk of future malfunctions. Best practices include:

• Replace or clean filters every 1-2 months during heavy use.
• Schedule annual professional tune-ups, including refrigerant checks.
• Ensure electrical connections are tight and protected from moisture.
• Clear outdoor units of leaves, debris, and pests regularly.

Most brands offer extended warranties if proof of maintenance is kept up to date.

AC Light Blinking Error Code References

Leading manufacturers publish online resources for error light codes.

• LG Error Code Guide
• Daikin AC Fault Codes List
• Mitsubishi Troubleshooting Tips

Compare your model’s blinking pattern to these official documents for a precise diagnosis.

The Role Of Circuit Boards And Sensors In AC Alerts

Modern air conditioners rely on advanced electronics. Printed circuit boards (PCBs) interpret sensor feedback to decide if an alert is necessary.

• Open thermistors or sensor disconnects create immediate red-green alerts.
• Surge protectors and relays protect the board from damage but may temporarily trigger blinking lights.

Upgrading to a surge protector or whole-home voltage stabilizer can help prevent error signals from electrical events.

What To Do If Your AC Won’t Start After Blinking Lights

If the AC remains inactive, follow this protocol:

1. Power cycle the system fully—main breaker and unit switch.
2. Wait at least 10 minutes for full board reset.
3. Check for error codes on your thermostat or display panel.
4. If available, consult mobile app diagnostic tools for smart ACs.

If the unit still fails, the problem may be with the control board, compressor capacitor, or wiring harness.

How Seasonal Changes Affect AC Alerts

Spring and summer bring out hidden AC issues:

• Rapid startups after winter can highlight capacitor or relay weaknesses.
• Unusual humidity increases the risk of sensor or pressure-related blinking lights.

Conduct a full system check before the cooling season and after major storms or power outages.

Energy Efficiency And Performance: Importance Of Responsive Fixes

Ignoring blinking lights can reduce AC efficiency by up to 30% as the unit compensates for sensor errors or blockages. Rapid troubleshooting maintains comfort and lowers energy bills.

• Verify the programmable thermostat settings after every reset.
• Upgrade to smart thermostats for early alert notifications via mobile apps.

Frequently Asked Questions On Blinking AC Lights

Question	Answer
Can I fix blinking lights myself?	Check simple issues like filters and reset the unit, but leave complex electrical fixes to a professional.
Does blinking mean my AC is broken?	Not always, but flashing lights do require attention before operating your unit further.
Will error lights reset on their own?	Some maintenance alerts auto-clear, but fault codes for electrical or refrigerant issues remain until addressed.

Summary And Best Practices

• Red and green light blinking on AC units are warning signals—they help prevent greater system damage.
• Quick action can solve many issues and protect long-term system health.
• When in doubt, consult the manufacturer guide or a licensed technician for accurate diagnosis.
• Regular maintenance prevents most common causes and saves on repair bills.