A flashing light on a heat pump is the system trying to tell you something. It may be on the outdoor unit’s control board, on the indoor air handler, or on the front of a ductless head. Here is how to read it and what to do next.
Where the light is
- Outdoor unit board. Behind the service panel on many heat pumps, often part of the defrost or control board. Do not open the panel with the power on.
- Indoor air handler board. Visible through a small window in the door on many units.
- Ductless indoor head. The row of small lights on the front of the unit.
- Thermostat. Some communicating thermostats show the code on screen.
Codes are specific to your brand and model
Like furnaces, heat pumps use different patterns by manufacturer and model generation. Ductless systems from Mitsubishi, Daikin, Fujitsu, Gree, Cooper and Hunter and others each use their own blink or error code tables. The right chart is in your installation or owner’s manual, often on a label inside a service panel or inside the front cover of a ductless head. Do not rely on a generic list online.
How to read it
- Do not reset the power first. Many systems clear the code when power is cycled.
- Count the flashes and note any pause pattern. Watch several full cycles.
- Note which light is flashing on units with several, and its color.
- Record a short video on your phone.
- Write down the model number from the rating plate.
What the patterns commonly point to
Without replacing your own chart, heat pump codes usually fall into a few groups:
- Normal operation or standby. Many boards blink slowly or glow steadily to show they have power. A green light blinking slowly is often normal.
- Timer or defrost indication. Some boards flash differently during the compressor delay or defrost. See defrost explained.
- Pressure faults. High or low pressure switch trips, often from a dirty outdoor coil, a failed fan motor, restricted airflow or low refrigerant.
- Sensor faults. A failed coil, outdoor air or discharge temperature sensor.
- Communication faults. On ductless and communicating systems, the indoor and outdoor units cannot talk, often from wiring issues.
- Lockout. The system has tripped a safety several times and shut itself down to protect the compressor.
What you can safely do
- Replace or clean the filter. On ductless heads, rinse the filters.
- Clear debris around the outdoor unit and check the coil is not packed with dirt or leaves.
- Check for ice. See heat pump freezing up.
- Check the breaker and outdoor disconnect.
- After you have recorded the code, one power reset is reasonable if the manual suggests it.
When to stop
If the same code returns after a reset, or the unit locks out, the system is protecting its compressor. Repeatedly resetting a lockout can turn a pressure switch or sensor problem into a compressor failure. Call instead.
What we do
Send us the code, the video and the model number, and we can often bring the likely part on the first visit. We confirm the fault with pressure and electrical readings. Our diagnostic is a flat $69 and it is credited toward the repair. Related: furnace light codes, heat pump not turning on, and our heat pump services page.
Frequently asked questions
Why is the light flashing on my heat pump?
It is a diagnostic code or status indicator from the control board. The meaning depends on your brand and model, so check the chart in your manual or on the unit.
Is a blinking green light on a heat pump normal?
On many boards, a slow green blink or steady light means normal operation or standby. Confirm with your model’s chart.
What do flashing lights on a mini-split mean?
Ductless indoor heads use blink patterns or error codes that are specific to the manufacturer. Record the pattern and model number and check the manual.
Should I reset my heat pump when the light flashes?
Record the code first, since a reset often clears it. One reset is reasonable. If the code returns, have it checked instead of resetting again.
What does a heat pump lockout mean?
The system tripped a safety several times and shut down to protect the compressor. It needs a technician to find the cause.
Can a dirty filter cause a heat pump error code?
Yes. Restricted airflow can trigger pressure or temperature faults in both heating and cooling.