Mitsubishi MR. Slim air conditioner error codes

Mitsubishi mr. Slim air conditioner error codes

Troubleshooting for Mitsubishi air conditioners based on the results of self-diagnostics.

The modern air conditioners from Mitsubishi have a very developed self-diagnostics system, and when the control system detects an error, it blocks the operation of the entire device and displays a cause of faulty condition.

The control system of the Mitsubishi air conditioners reports that an error occurred by blinking of a light-emitting diode on the surface of the internal (or external) unit. When a particular error of an air conditioner is detected, light-emitting diodes blink in a certain order, which corresponds with a particular error. If the control system of an air conditioner detects more than one error, the error with the highest priority is displayed first and then all the following errors are displayed

After completing installation and the wiring and piping of the indoor and outdoor units, check for refrigerant leakage, looseness in the power supply or control wiring, wrong polarity, and no disconnection of one phase in the supply.

Mitsubishi e9 error code

Mitsubishi e9 error code

The E9 error indicates poor communication between the indoor and outdoor units. If you see it on your AC’s display, do the following:

  • Check the wires connecting the two units and make sure all their parts are compatible;
  • When installing the unit, check all connections prior to powering it up. Be sure they are CORRECT! Incorrect connection may cause damage to the control board. Please, read the manual very carefully and refer to it when installing the AC. Follow all instructions and illustrations. The indoor unit should get power from the outdoor one; Mitsubisi units require alternate current. Check polarity before running the unit. In alternate-current devices, failure to follow the polarity will not prevent the indoor unit from running, but there will be a communication failure between the two units. In direct-current units, improper polarity will result in the indoor unit not working at all.
  • Be sure that no condensate pumps are connected to the terminals of the indoor unit.
  • If none of these issues are detected, call a technician and have control boards checked and replaced, if necessary.

Mitsubishi p2 error code

Mitsubishi p2 error code

If you see a P2 fault code on your AC’s display, chances are you can fix it yourself providing that you have a little technical skill. If not, it is better to address a qualified technician anyway.

Here is a brief troubleshooting guide on the P2 error code:

What Does a P2 Error Code on a Mini Split Denote?

If you look it up in your manual, you will find that the main control board has detected an overheat in the compressor and the system is trying to protect it from total failure.

Why a Mini Split May Overheat?

  • Poor ventilation
  • Lack of refrigerant
  • Sensor failure
  • Main PCB board failure

The main PCB signals an overheat and prevents compressor damage by sending out the P2 error code and stopping the system’s work.

The signal is sent by an overload protector sensor, which is attached to the compressor. The error may be caused by a number of factors and there are ways to fix the problem:

The P2 Troubleshooting Guide

  1. Check the ventilation system for blockages. Be sure that the impeller is spinning smoothly and there are no foreign objects or debris blocking it.
  2. Try resetting the AC: turn off the unit, disconnect it from the mains, wait for about 10 to 15 minutes, reconnect and turn it back on.
  3. The temperature at the compressor’s top should not exceed 212F/100° If it does, the PCB will send the error and stop the unit’s operation.
  4. Check the refrigeration system for leaks.
  5. Make sure there is enough refrigerant in the system.
  6. Make overload protector sensor is not faulty.
  7. Make Outdoor Main PCB Board is not damaged orr faulty. If it is, take steps to replace it.

Mitsubishi p4 error code

Mitsubishi p4 error code

The P4 error code signals a drain sensor failure

What causes it:

  1. Transmission wire disconnection
  2. Thermistor failure


  1. Be sure the connector is not loose.
  2. Check the thermistor ➃ – ➄ for continuity.

If the continuity is ok, install a new indoor controller board.

Mitsubishi u3 error code

Mitsubishi u3 error code
The U3 code appears when there is a problem with the capacitor, unstable current or faulty varistor. The metal oxide varistor is an element, which protects the system against power surges. Therefore, a varistor failure can expose the wiring and other components to the destructive influence of power ups. Please, take steps to fix the problem ASAP!

Mitsubishi error code 1301

Mitsubishi error code 1301

This error code signals a low pressure fault

While the head pressure may drop, it may rise in the suction area, near the heat pump or compressor.

The system may continue to cool at a lower capacity with the coil temperature dropping by around ten degrees. Most commonly, the head pressure at the conditioning unit or heat pump compressor motor falls due to the following factors:

  • The system has gotten low on refrigerant due to improper charging or a leak.
  • Improper refrigerant metering due to a TXV (TEV) fault. This is not about smaller ACs or heat pumps, because they feature a capillary tube. Also, improper metering may result from installation of a too short or too large cap tube.
  • In some cases, the head pressure drops due to faulty leaky compressor motor valves, which won’t let the compressor pressure reach the needed level. The valves may go faulty due to an overcharge, poorly calibrated TXV, or other factors that cause the refrigerant stagnate at the compressor. This also happens to accumulation of acid and sludge contamination and consequently, blockages, which may cause the coolant to get into the compressor and ruin valves.
  • Piston rings in the compressor motor or on a rotary compressor and/or seals have worn out. The problem needs to be solved ASAP because low head pressure leads to poor lubrication in the motor and, consequently, premature wear of motor parts and compressor damage. Low high side pressure and poor cooling capability can be signs of this wear.
  • There may be leaks in the oil separator return line
  • Not uncommonly, the head pressure occurs due to compressor motor overheating. Most technicians say that it is one of the most serious issues, which should be solved ASAP. If left untreated, it will lead to serious damage and premature death of the device.

Mitsubishi error code 5102

Mitsubishi error code 5102

The 5102 error code occurs in the following cases:

  • Failing pipe temperature sensor (TH22) in the indoor unit;
  • Failing pipe temperature sensor (TH2) in the OA processing unit.

Fixing it

If the thermostat is on and when there is an open- or short circuit, the outdoor unit will restart after 3 minutes only. If the error disappears after 3 minutes, the unit will operate well. If it does not, the unit will stop.

A short- and open circuit can be detected within a particular temperature range:

There is a temp range, within which a short and an open are detectable:

  • 194°F [90°C] or higher for short
  • -40°C [-40°F] or lower for open

The system will not detect a sensor failure at gas-side within these temp ranges.

Mitsubishi error code 5701

Mitsubishi error code 5701

The 5701 error appears due to a problem with the humidity sensor or temp sensor.

What can I do about it?

  1. Be sure that the connector CN22 on the circuit board is not loose or damaged.
  2. Be sure that the outside humidity sensor and relay cable are properly connected.
  3. Check the humidity sensor’s (CN22) output voltage across 2P and 4P