Mitsubishi air conditioners are some of the most reliable aircon units. In addition, they are easy to install because Mitsubishi includes a complete installation kit for each AC unit. They are also extremely flexible, boast superior energy efficiency, and are known for whisper-quiet operation.
Unfortunately, as with all air conditioners, a few things go wrong sometimes. For instance, the dreaded refrigerant leak can leave you lost in the wild. The refrigerant leakage is caused by dirty air filters, frozen coils, blocked outside units, and broken parts, such as broken fans, which are also not uncommon.
Mitsubishi air conditioners are designed to blink red or green lights several times to alert or warn users about some of these issues. And so if you see 2 green lights on your Mitsubishi mini split system, you might be wondering what it means.
What are the 2 Green Lights on Mitsubishi Mini Split?
If you see 2 green lights on your Mitsubishi unit, the mini split has not yet reached the set temperature, and it’s working to cool or heat your room. The indoor unit sensors are intuitive and will identify temperature drops or increases over 2°C from the set temperature of your mini split.
However, two blinking green lights on your Mitsubishi air conditioner often mean the bottom louver’s clasp isn’t firmly shut. It could also signify a bigger issue depending on the number of flashes.
Once you have noted the number of blinks per set, refer to the error code list provided by Mitsubishi electric (check the bottom of your wall unit for the model number)
What Are AC Error Codes?
The flashing lights are part of the error codes that HVAC systems use to alert users of a possible appliance malfunction.
An error code is essentially a signal. It’s a built-in mechanism that allows electrical devices to alert users of a potential appliance malfunction.
Error codes serve three main functions;
- Alert you about malfunction: The flashing green light, for instance, is a signal that your air conditioner is not working normally because of an underlying problem.
- Give a hint about the underlying problem: Diagnosing air conditioner issues is a massive challenge, especially when you don’t know where to begin. The diagnostic codes give you a clue where the problem lies, so you know where to begin troubleshooting.
- Let you know when you’ve fixed the original problem: Error codes go away automatically once you’ve fixed the underlying problem. That way, you know that you’ve successfully fixed the original problem.
Do All AC Brands Have Error Codes?
Yes, all the major AC brands have error codes because manufacturers benefit when users can self-diagnose and fix basic air conditioner issues.
For instance, if the unit is blinking because the door isn’t shut tightly, isn’t it better to have users fix the issue themselves than call the manufacturer to report the problem in the middle of the night? It significantly reduces customer support costs.
Of course, it’s also easier for the manufacturer to handle repair requests. The user seeking repairs will report the symptoms and the error code, allowing the manufacturer to send the right team with the right equipment for faster troubleshooting and repair.
However, remember that different manufacturers use different error codes. For example, some use green blinking lights, others red lights, and others letters and numbers on the remote control. Meanwhile, others use a combination of two or more code types. Therefore, it’s helpful to learn about your AC manufacturer’s AC codes early.
What Do Two Green Lights on a Mitsubishi Mini Split Mean?
It depends on whether the lights are solid or blinking. So, the first step is to observe the light for at least five seconds.
Solid Green Lights
If the AC has two solid green lights, you don’t have to worry, as it merely indicates that the air conditioner is working hard to condition your room but is still a long way from reaching the remote thermostat setting.
This usually happens when the weather is very hot, forcing the AC to work harder than normal to blow cool air in cool mode.
Alternatively, it may happen if you’re just turning on the air conditioner in a hot and humid room. In dry mode, your Mitsubishi mini-split should dehumidify the room without cooling your home
Mitsubishi split systems respond to the two solid green lights by ramping up heat removal.
For instance, the AC will increase the fan speed to remove heat faster.
After some time, you’ll notice that one of the green lights goes off, so you’re only left with one solid green light. This is a sign of progress on the original problem. It means that the air conditioner has managed to drop indoor temperatures to within two degrees of the thermostat setting.
At this point, your Mitsubishi air conditioner will slow down operations to save energy and prevent hot air blasts. For instance, the built-in fan will slow down for gentler air circulation.
Blinking Green Lights
If your Mitsubishi air conditioner has two blinking green lights, either the clasp on the aircon’s bottom louver isn’t shut tightly or the unit has a bigger problem, such as miswiring, a non-operational outdoor unit, a bad thermistor, or a damaged fan motor.
What to do when your Mitsubishi AC Blinks 2 Green Lights
We recommend that you begin by ruling out the most obvious issues and working your way to the most technical ones.
Check the clasp of the aircon’s bottom louver
The most common cause of two blinking green lights on a Mitsubishi mini split air conditioner is an open or loosely closely bottom louver.
The bottom louver has slats that allow air and light to enter the unit while keeping out rain and direct sunlight.
Thus, leaving the bottom louver open or loosely closed can impact airflow within the unit, potentially impacting pressure and sensors within the unit. Unfortunately, that’s what happens when the clasps are not tight enough.
Mitsubishi air conditioners prevent the potential consequences by suspending operation and continuously flashing two green lights until you shut the louvers correctly.
So, shut down the AC, put back the clasps, then turn the AC back on to see if the problem is solved. If it resumes normal operation, the bottom louver was previously open.
Determine the Blinking Pattern (Watch and Note)
However, if the problem persists even with the bottom louver shut correctly, you likely have a bigger problem. You need to note the blinking pattern to establish the root cause.
Get close to the indoor units and observe the blinking lights for several seconds, counting how many times it blinks before pausing.
Typically, it flashes once every second for several flashes, then pauses for 2-3 seconds before resuming the flashing. So you need to count the number of flashes between the pauses and note the number somewhere.
Refer to the Unit’s Cover or Manual
Once you’ve identified the blinking pattern, the next step is to cross-check with the aircon’s manual to find out what the pattern means. Modern Mitsubishi air conditioning units have a list of error codes on the unit’s cover.
Alternatively, check Mitsubishi’s online error code list or call the Mitsubishi customer support desk to ask what the error code means.
Decoding Common Mitsubishi Blinking Light Error Codes
The following are the eight most common error codes (two green flashing lights) on Mitsubishi mini-split air conditioners.
If the two green lights blink continuously with no breaks, your Mitsubishi air conditioner is either wrongly wired (indoors or outdoors) or has a serial signal issue.
Mis-wiring may mean that one or more thermostat wires are connected to the wrong terminal or the connection at a terminal is loose or disconnected.
Solution: Diagnose the wiring and poor connection at the terminal. If the wiring is fine, diagnose the indoor and outdoor PC boards.
Operation Light Flashes 2x
If the two green lights blink twice between pauses, there’s a problem with your indoor air handler thermistors. Either the thermistors are shorted, or their circuits are open.
Thermistors (thermal resistors) are temperature-dependent resistors that change resistance with a temperature rise when in heat mode. They are very sensitive and therefore help air conditioners (and heat pumps) react to the tiniest temperature changes.
Solution: Troubleshoot the indoor thermistor. Is it working? Is it working accurately? If yes, troubleshoot the indoor printed circuit board (PCB).
Operation Light Flashes 3x
If the green lights flash three times in between pauses, there’s a problem with the indoor fan. In most cases, it’s a sign that the fan isn’t generating the rotational frequency (number of revolutions per second) necessary to keep the unit running.
Solution: Diagnose the indoor air handler fan. Is it covered in dirt/dust? Are some of the fan blades broken? Is the motor dead? Clean the air filter once every two weeks. Use a vacuum to remove dirt from the air filter and avoid touching the metal part to avoid injuries.
Operation Light Flashes 4x
The operation flashing light four times usually indicates a problem with the indoor control board. For example, perhaps the PCB isn’t transmitting electric signals, or some of the board’s components are faulty or unresponsive.
Solution: You’ll need to troubleshoot the indoor board to determine the cause of the problem. We strongly recommend hiring an HVAC professional for this job.
Operation Light Flashes 5x
Five flashes of the operation light are often signs of a power system problem. Common issues include a loose or disconnected compressor wire, an issue with the inverter output voltage, or wrong compressor resistance winding. A spike in the power supply can play havoc with them
Solution: You need to troubleshoot the outdoor AC unit’s power system. Why is it not working normally?
Operation Light Flashes 6x
Six flashes of the operation light are signs of issues with the outdoor thermistor. In most cases, the thermistor is compromised, therefore not responding accurately to temperature changes. Or maybe it’s not responding at all.
Solution: You need to troubleshoot the outdoor AC unit to determine what’s wrong with the thermistor. Is it dead? Is the filter dirty? Is it loosely connected?
Operation Light Flashes 7x
Seven flashes of the operation light are signs of problems with the outdoor PCB. Either the PCB isn’t responding to requests or is sending the wrong responses.
Solution: Could your outdoor printed circuit board be broken? Or does it have a significant dirt buildup that’s impacting the current flow?
Operation Light Flashes 14x
Fourteen flashes of the operation light denote “other problems” or abnormalities other than those mentioned above.
Solution: Refer to the service manual to find out more about issues that may cause fourteen operation light flashes.
What to do when the Blinking Lights Persist
- Reset the system: Turn off the AC at the indoor unit and then at the breaker. Then wait at least 30 seconds, and turn the unit back on (at breaker then indoor unit). Does it work now?
- Call an experienced technician: If resetting the unit doesn’t fix the problem, it’s time for professional troubleshooting. Switch off the AC at the indoor air handler and call your HVAC technician.
Mitsubishi Mini Split Troubleshooting Guide
Mitsubishi Mini-Split Keeps Shutting Off
If the AC unit keeps shutting off, you should check the following:
- Are the evaporator coils frozen? This may happen due to blocked airflow.
- Is the refrigerant level sufficient?
- Could the compressor be overheating perhaps as a result of debris? Mitsubishi mini split troubleshooting guide – noise issue Mitsubishi mini-split hissing sound. This is routinely the sound made when the refrigerant flow (inside the AC) is switched so it mostly does not point to a malfunction. Mitsubishi mini-split clicking noise. This sound is most generated during the contraction/ expansion of the plastic parts including the front panel, etc. as the temperature changes.
Why is my Mitsubishi AC light blinking?
The blinking light is a built-in self-diagnosis mechanism that lets users quickly learn about potential issues with their units and helps users and technicians easily troubleshoot the underlying issue.
Why is my Mitsubishi AC blinking green?
It depends on the number of blinks. If it blinks continuously, check that the clasp of the bottom louver is shut tightly. Otherwise, count the number of flashes and cross-check with the Mitsubishi service manual.
How do I turn off the light on my Mitsubishi aircon?
First, make sure the clasp of the bottom louver is shut correctly. If so, reset the AC. Call an HVAC technician to troubleshoot the problem if that doesn’t work.
How do I find my Mitsubishi AC error code?
There are two ways. For modern Mitsubishi mini split air conditioners, check under the cover. You’ll find a list of error codes and what they mean. Alternatively, check the printed or online Mitsubishi service manual.
How do I fix an AC error code?
Begin by resetting it to see if the problem goes away. Different mini splits are reset differently, so you’ll need to know how to reset your unit. Note down the error code and call an HVAC technician if resetting doesn’t work.
That’s all you need to know about two green lights on Mitsubishi mini splits and Mitsubishi error codes in general. If the outside compressor runs and the inside unit blows air but doesn’t cool in cooling mode (or if it’s a heat pump mode and also doesn’t heat in heating mode).
Then the refrigerant wasn’t installed or there is a bad control board or module. The coils, refrigerant lines, and flare connections should be regularly inspected for leakage.
Don’t hesitate to contact an HVAC technician if you’re unable to troubleshoot the issue behind the flashing lights or run into more challenging problems.