P8 Code On Mitsubishi Mr. Slim—What Does It Mean? How To Fix?

You tried turning on your Mitsubishi Mr. Slim ductless split AC, but it gave you a P8 error message. What does this code mean, and what can you do to fix it? We researched these concerns for your convenience, and here’s what we found.

A P8 error code on a Mitsubishi Mr. Slim ductless AC usually means it encountered an error with the outside condenser unit. The source of the issue can come from different sources. You may diagnose the cause of the error message by looking at how the LEDs on the outdoor PC board act. Some examples are:

  • Flashing LED 1: Compressor Command Phase Detected
  • Flashing LED 3: Operation Sensor Short Or Open
  • Flashing LED 6: 4-Way Valve Is On Switch 26C

Keep reading as we talk about these possible errors in greater detail. We’ll also tackle the potential solution you can take advantage of for each likely cause as you go through this post.

Air conditioner (AC) indoor unit or evaporator and wall-mounted. That is part of mini split system or ductless system type. For removing heat and moisture from room. Including humidity control, P8 Code On Mitsubishi Mr. Slim - What Does It Mean How To Fix

What Does The P8 Error Code Mean On A Mitsubishi Mr. Slim Split AC?

When a P8 error message appears on your Mr. Slim's remote, you need to take a look at the outside condenser’s PC board. Here, observe how the LEDs behave. Doing so may help you find the cause of the problem.

2019 Wall hung Mitsubishi ductless mini split system being inspected for summer air conditioning operation.

Some possible reasons that promote the P8 code are:

Flashing LED 1: Compressor Command Phase Detected

This particular issue generally occurs because of an improper installation of the Mr. Slim AC. In particular, the AC’s electrical setup uses a 3-phase framework. But one of the phases is either missing or wired wrongly.

Take note that a 3-phase electrical framework generally often works if the system has proper wiring. That way, each phase can accommodate the relatively high load presented by the air conditioner.

How To Fix

Rewiring the outside condenser’s motor may help remove the P8 error message and restore the AC’s normal functions. Make sure you have sufficient electrical experience and know-how before you proceed with this task. Otherwise, request the help of a seasoned technician in the industry.

Nonetheless, follow these general steps if you want to proceed, especially if you’re connecting the Mr. Split AC to a 1-phase power supply:

Step-By-Step Guide

  1. Make a U1 connection to the AC's motor to the correct terminal on the capacitor.
  2. Connect the positive terminal from your home’s electrical network to the motor to the capacitor.
  3. Create a V1 connection from the AC's motor to the connection made in the previous step.
  4. Create a W1 connection from the AC’s motor to your home’s electrical network through its negative terminal.

Make sure that each connection made is secure. Loose wiring may result in the P8 error message persisting. You can also watch the video below if you need a visual guide to the steps mentioned above:

Flashing LED 3: Operation Sensor Short Or Open

A P8 error message accompanied by a flashing 3rd led on its outside PC board typically means a high-pressure safety issue. It means that the outdoor condenser unit is experiencing abnormally high pressure. This problem may occur because of different reasons, such as a bad fan motor or a corroded refrigeration circuit.

How To Fix

Female hand holding remote control of the air conditioner

Troubleshoot the Mr. Slim’s outside condenser unit to find the main cause of the issue. You may also need to check the indoor air handler if needed. For example, if the blower or fan motor is at fault, perhaps the best solution is to replace the faulty unit with a new one.

Keep reading to gain additional insight on how to replace a Mr. Slim fan motor, which may potentially solve the P8 error code issue:

What You’ll Need

  • Screwdriver
  • Allen or hex wrench
  • Replacement fan motor

Step-By-Step Guide

  1. Turn off the AC from its connected circuit breaker.
  2. Remove the air handler’s front panel.
  3. Remove the electrical box carefully.
  4. Detach the drain hose.
  5. Take out the nozzle assembly carefully.
  6. Remove the hex screw from the line flow fan and the blower motor.
  7. Remove the screws affixing the heat exchanger.
  8. Open the heat exchanger’s cover slightly.
  9. Pull out the old fan motor and install the new unit.
  10. Go through the steps in reverse order to reassemble the Mr. Slim AC.
  11. Turn on the AC to check if the error code persists.

Check out this replacement Mitsubishi AC fan motor on Amazon.

You may also watch this video if you need a visual guide for this procedure. While the following clip isn't in English, the people performing the replacement task do a good job of displaying the steps needed to change a Mr. Slim’s fan motor:

Flashing LED 6: 4-Way Valve Is On Switch 26C

A discharge thermistor might be causing the P8 error message to appear. But the main cause of this issue might be from low refrigerant or the assembly is faulty.

How To Fix

Troubleshoot the thermistor and its nearby components to find the main cause of the P8 code. Then, you may proceed with the fix by following the appropriate steps based on your findings.

For instance, follow these steps if you need to recharge the Mr. Slim AC and remove the P8 error message:

What You’ll Need

  • Manifold gauges
  • AC refrigerant

Step-By-Step Guide

  1. Turn off the AC from its connected circuit breaker.
  2. Connect the blue hose to the outside condenser unit’s access port.
  3. Connect the yellow hose to the AC refrigerant container.
  4. Open the refrigerant container and open the valve marked “Low” slowly.
  5. Close the Low valve once the gauge’s needle reaches about 120 PSI.
  6. Repeat steps 4 and 5 until the needle stays in the recommended spot.

Check out this digital AC refrigerant pressure reader on Amazon.

You can also watch this video if you need a visual guide for this procedure:

How Long Does A Mitsubishi Mr. Slim Last?

Air conditioner (AC) indoor unit or evaporator and wall-mounted. That is part of mini split system or ductless system type. For removing heat and moisture from room. Including humidity control.

Generally, split ACs, including the Mitsubishi Mr. Split, may last about 8 to 18 years. However, the appliance’s lifespan may depend on different factors. Routine care and maintenance are crucial for extending your AC's lifespan.

Watch the video below if you need help maintaining a ductless split AC:

You might also be wondering how long does a Bryant air conditioner last. If so, follow that link to know the answer.

2 Alternatives to Mitsubishi Mr. Slim

Wall mounted air conditioner that is installed in the bedroom.

At this point, you might be looking into replacing your Mitsubishi Mr. Slim. This thought may come to mind if the cooling unit is giving you frequent problems, including the P8 code. If so, here are some excellent candidates for your next ductless split AC:

1. Senville SENL-09CD-16 LETO Mini Split AC And Heat Pump

Senville’s offering introduces smart AC features to households that want them. One feature that’s worth mentioning is the Alexa-enabled commands. With it, users can use voice commands through Amazon’s proprietary AI to control the AC from afar.

Another feature brought by this particular mini split AC is its built-in heat pump. That way, users can take advantage of this device’s cooling and heating capabilities regardless of the current season.

Check out this product on Amazon.

2. Cooper & Hunter Ductless Mini Split AC

Homeowners and guests that might find it annoying to listen to AC motors may want to check out this product. This particular mini split AC takes advantage of the brand's whisper technology. The feature promotes quiet operations, which might also be ideal for commercial applications.

This AC is also Wi-Fi compatible, which means you can control its functions with an app. However, the standard package doesn’t include a Wi-Fi dongle. You need this component to make the AC communicate with your smartphone wirelessly.

Plus, if you purchase this AC from a reliable retailer, you may also take advantage of a limited warranty. The unit may also come pre-charged with a sufficient amount of refrigerant.

Check out this product on Amazon.

Final Thoughts

Don’t attempt to fix your Mitsubishi Mr. Slim without troubleshooting the cause of the P8 error code first. Once you find the cause, use the appropriate DIY measures to fix the problem at its source. If you believe you don’t have the confidence, experience, or skill to complete the required task, consult the help of a reliable AC technician.

If you’re looking for answers to other Mitsubishi Mr. Slim concerns, check out these other posts:

Mitsubishi Mr. Slim Is Leaking Water – What To Do?

Mitsubishi Mr. Slim Not Responding To Remote – Why? What To Do?

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