Technical Service Manual

Contents

This document provides technical service information for the dishwasher, including specifications, water circuit details, component theory of parts, test programs, error codes, and troubleshooting guides.

• Specifications
• Water Circuit
• Location & Theory of Parts (PCB, Inlet Valve, Drain Pump, Heater, Washing Pump, NTC, Flowmeter, Safety Hose)
• Test Program
• Error Codes
• Troubleshooting

Specifications

Electrical Supply: 220-240V, 50Hz

Supply Water Pressure: 0.04MPa-1.0MPa

Supply Water Temperature: Below 60°C

For basic operation instructions, please refer to the instruction manual attached with each unit.

Water Circuit

Diagram illustrating the water circuit scheme. Key routes are indicated by colors: Magenta for Inlet water route, Blue for Drain water route, and Cyan for Cycle water route.

Function Description

Process of water inlet (indicated by magenta route): In this process, the regeneration water route is cut off, and the main water route is open. Water is softened by the softener before entering the tub. Some inlet water is stored in the air breaker for regeneration.

Process of cycle washing (indicated by blue route): The washing pump motor drives the cycle washing action. Water is pumped through the washing pump, then to the spray arms, out through the nozzles onto the dishes, into the sump, and back to the washing pump for the next cycle.

Location & Theory of Parts

Diagram showing the internal layout of the dishwasher with key components labeled: Inlet valve, Washing Pump, Heater, Main PCB, Drain Pump, Softener.

Note: Exploded views and part lists may vary slightly between models. Refer to the latest documentation provided by Midea.

PCB (Printed Circuit Board)

The PCB serves as the control center, receiving and processing signals from components, sending commands, and managing feedback.

Accessing the PCB

The PCB is located within a protecting box at the bottom of the machine. Steps for removal include:

1. Disconnect power supply.
2. Remove cutlery basket, main basket, and filter system.
3. Remove the protecting box.
4. Remove screws securing the PCB to the protecting box.
5. Disconnect the connector from the PCB.
6. Remove the PCB.
7. Reverse the procedure for installation.

Diagram of the PCB with components and connection points labeled. A table lists components by number and mark, with their functions:

Note: Component placement may differ slightly between models, but the markings on the PCB have consistent meanings.

Inlet Valve

Location: Shown in the bottom view diagram.

Appearance: Diagram shows terminals, connection to air breaker, and electric coil inside.

Work Principle: An electromagnetic valve that controls water entry. When signaled by the controller, it opens to allow water in. It consists of an electric coil, valve body, valve pole, and filter.

Defeat Points & Errors:

• Valve coil broken: Prevents opening, causes E1 error.
• Filter jammed: Prevents water entry, causes E1 error.
• Loose connector: Prevents opening, causes E1 error.
• Valve pole rusted/locked: Prevents opening/closing, causes E1 or E4 error.

Technical Data:

Accessing the Inlet Valve:

1. Disconnect power.
2. Remove the water inlet hose (caution: residual water may drip).
3. Remove the bottom board cover.
4. Disconnect the 2 terminal lugs from the inlet valve.
5. Gently pull and twist the valve to remove it.
6. Remove the clamp and disconnect the inlet hose to the air breaker.
7. Reverse for installation.

Inspecting the Inlet Valve:

Check Electric Part: Measure resistance between blue wire (EV1) and blue wire (ACN) using a multimeter. Normal resistance is approx. 4.4kΩ to 4.8kΩ. Incorrect resistance indicates a broken coil or loose connector.

Check Machine Part: Inspect the valve filter for blockages. If clear and water still doesn't enter, check valve operation. If it fails to act, replace the valve. If water continuously enters, replace the valve.

Drain Pump

Location: Shown in the bottom view diagram.

Work Principle: Consists of an electrical motor, impeller, inlet, and outlet. Driven by a permanent magnet synchronous motor with low rotor inertia.

Defeat Points & Errors:

• Motor coil broken: Pump won't work, causes E1 error.
• Weak motor rotor magnetism: Pump won't work, causes E1 error.
• Loose connector: Pump won't work, causes E1 error.
• Rotor locked by residues: Pump won't work, causes E1 error.
• Loose drain pump assembly rack: Causes noise.
• Bad non-return valve: Retains water.

Explanatory notes: A drain pump failure can lead to an E1 error because if water isn't drained, the pressure switch may cut off the inlet valve, preventing new water entry.

Technical Data:

Accessing the Drain Pump:

1. Drain water and disconnect power.
2. Remove the bottom board cover (loosen top hooks first, then side hooks).
3. Label and disconnect the two terminal lugs.
4. Twist the drain pump to remove it.
5. Reverse for installation.

Inspecting the Drain Pump:

Check Electric Part: Measure resistance between red wire (PS) and blue wire (ACN). Normal resistance is about 220Ω to 250Ω. Incorrect resistance indicates a broken coil or loose connector. If resistance is OK but it doesn't work, the magnetism might be too weak.

Check Machine Part: Check the non-return valve if it's assembled incorrectly, causing water retention. If the pump runs but doesn't drain, check the drain hose or drain body.

Heater

Location: Shown in the bottom view diagram.

Work Principle: Consists of a fuse, heater, and pressure switch.

Technical Data:

Defeat Points & Errors:

• Heater coil broken: Heater won't work, causes E3 error.
• Fuse is active: Heater won't work, causes E3 error.
• Loose connector: Heater won't work, causes E3 error.

Accessing the Heater:

1. Drain water and disconnect power.
2. Remove bottom board.
3. Label and disconnect terminals.
4. Remove 2 clamps fixing pump hoses (caution: clamps are single-use).
5. Twist the upper pump to remove it.
6. Reverse for installation.

Inspecting the Heater:

Measure resistance between the two terminals. Normal resistance is about 27Ω to 30Ω. Incorrect resistance indicates a broken heater coil or thermostat.

Washing Pump

Location: Shown in the bottom view diagram.

Work Principle: An asynchronism motor with a capacitor, featuring a stator with silicon steel stack and two coils (main and assistant).

Defeat Points & Errors:

• Motor coil broken: Pump won't work, causes E3 error.
• Weak motor rotor capacitor: Pump won't start, causes electromagnetism noise. Thermal protector may engage, causing E3 error.
• Loose connector: Pump won't work, causes E3 error.
• Rotor locked by residues: Pump won't work, causes E3 error.
• Loose drain pump assembly bracket: Causes noise.
• Machine unused for long time: May prevent pump starting.

Technical Data (Model: YXW50-2E):

Accessing the Washing Pump:

1. Disconnect power.
2. Remove bottom board.
3. Label and disconnect terminals.
4. Remove 2 clamps fixing pump hoses (caution: clamps are single-use).
5. Twist the upper pump to remove it.
6. Remove the screw fixing the impeller to the pump.
7. Remove 2 screws fixing the lower pump to the motor.
8. Reverse for installation.

Inspecting the Washing Pump:

Check Electric Part: Measure resistance between ML-H and ACN (normal: 100Ω to 130Ω) and between ML-H and ML-L (normal: 350Ω to 450Ω). Incorrect resistance indicates a broken coil or loose connector. If resistance is OK but it doesn't work, the capacitor may be weak.

Check Machine Part: Check pump assembly bracket for looseness (causes noise). If the pump won't start after long idle, the seal element might be bonded. If the drain pump works but drains little, check the vane wheel.

NTC (Negative Temperature Coefficient Thermistor)

Location: Integrated into the sump.

Work Principle: Measures the temperature of water in the tub.

Accessing the NTC:

1. Remove bottom board.
2. Remove two screws securing the NTC to the sump.
3. Take out the NTC.
4. Reverse for installation.

Inspecting the NTC:

Measure resistance between the RE and GND wires using a multimeter. Refer to the NTC resistance table for normal values at different temperatures.

Incorrect resistance indicates an NTC circuit problem. Check connections first; if unresolved, replace the NTC.

Flowmeter

Location: Integrated into the Air Breaker.

Work Principle: Measures water quantity. Water rotation of an impeller generates electronic pulses detected by a tongue tube.

Accessing the Flowmeter:

1. Remove baseboard, top panel, and left side panel.
2. Remove the plastic nut securing the air breaker to the tub (replace air breaker if flowmeter fails).
3. Disconnect the wire and remove the clamp fastening the hose to the air breaker.
4. Take out the air breaker.
5. Reverse for installation.

Inspecting the Flowmeter:

Use a multimeter's diode setting to test between the black wire (FM) and blue wire (GND) while water is passing. Continuous electrical pulses (indicated by sound) confirm normal operation. No pulse indicates a flowmeter circuit issue; check connections, then replace the air breaker if necessary.

Safety Hose

Location: Shown in diagrams.

Work Principle:

• Mechanical Aquastop Hose: Two layers. Water leak causes foaming material to expand and lock the hose, potentially triggering an E1 alarm.
• Electronic Aquastop Hose: Two layers. Water leak on the bottom tray activates a flooding pressure switch, causing an electromagnetic valve to cut off water, potentially triggering an E4 alarm.

Accessing the Safety Hose:

1. Remove baseboard, side baseboard, top panel, and left side panel.
2. Remove clamp, cut the bound belt, and disconnect the wire connector to pull out the inlet hose.
3. Reverse for assembly.

Inspecting the Safety Hose:

Electronic Aquastop Hose: Measure resistance between blue wire (EV1) and blue wire (ACN). Open circuit or short circuit is incorrect. Incorrect resistance suggests a broken valve coil or loose connector.

Mechanical Aquastop Hose: Moisture absorption in the foaming material can cause a non-resettable self-lock fault (prevents water filling).

Test Program

This program is designed to check component operation and diagnose malfunctions.

How to Activate Test Program

With the door open, within 60 seconds of powering on, hold the Start/Pause button and press the POWER button. The machine will enter Test Program mode and pause at step 00. Close the door to start.

During program running, the Start/Pause button can be used to jump to the next step (except for the inlet valve step).

Test Program Operation Summary:

Test Program Steps & Error Codes:

Note: Activation methods may vary slightly between models. Ensure the unit is switched off at the wall before starting the activation sequence.

Procedure of Test Program (for models controlling water filling by flowmeter)

Error Codes

This section details how to identify and understand error codes displayed by the appliance.

How to Know Which Error Code Has Occurred

Refer to the Test Program Operation table. For example, if error 1 occurs, a buzzer sounds for 30 seconds and "E1" is displayed. Other errors follow similarly. For error 7, ECO, 90min, and Rapid indicators flash simultaneously.

Table showing the relationship between indicator combinations (ECO, 90 min, Rapid, Cloud Wash) and specific error codes (E1, E3, E4, E6, E7, Ed).

Notice: The majority of models follow this regulation.

Attention

Priority level of E4 is the highest. E4 operation is valid only after other operations have completed. When E4 is done, other errors become invalid. In test programs, E1, E3, E4, E6, E7, Ed are valid.

How Does the Appliance React When Error Code Occurred

• E1 Water filling exceed pre-set time: If inlet valve is open for 4 mins but water quantity is insufficient, E1 occurs. Drain pump runs, other components stop. Buzzer alarms for 30s.
• E3 Heating exceed pre-set time: If heating element runs for 60 mins but temperature is not reached, E3 occurs. Drain pump runs, other components stop. Buzzer alarms for 30s.
• E4 Overflow: If overflow micro-switch activates for over 2 seconds, E4 occurs. Drain pump runs, other components stop. Buzzer alarms for 30s. (E4 has the highest priority).
• E6 Open-circuit failure of thermistor: Detected by the controller, E6 occurs. Drain pump runs, other components stop. Buzzer alarms for 30s.
• E7 Short-circuit failure of thermistor: Detected by the controller, E7 occurs. Drain pump runs, other components stop. Buzzer alarms for 30s.
• Ed Communication failure: If display board shows communication anomalies for 20 seconds, Ed occurs. Check display board connections.

Troubleshooting

This section provides diagnostic steps and solutions for common error codes and performance issues.

E1 Tree -> Inspection

E1 Code: Longer inlet time

• Is there any water in the Tub?
  • No water: Check Tap (open or not). If failure, open it.
  • Little water: Check inlet hose of AQUASTOP (if applicable). If blocked/kinked, solve the problem.
  • If inlet hose is OK: Check Inlet Valve circuit. If correct, proceed. If not, reconnect wire and check again. If still wrong, replace Inlet Valve.
  • Model with Flowmeter: Check Flowmeter circuit. If correct, proceed. If not, reconnect wire and check again. If still wrong, replace Flowmeter.
  • Model with Pressure Switch: Check Pressure Switch circuit. If correct, proceed. If not, reconnect wire and check again. If still wrong, replace Pressure Switch.
  • Make a check of the Hydraulic pressure (0.04-1.0MPa is ok).
  • Make a check of Drain Hose. If kinked/blocked, solve the problem.

If the problem persists after all inspections, the PCB may be malfunctioning. Replace PCB and test again.

E3 Tree -> Inspection

E3: Longer heating time

• Check water temperature in the tub:
  • High: Make a check of over heat proof heating Micro-switch. If failure, replace switch.
  • Low: Check whether the filter is jammed severely or not. If jammed, clear or replace filter.
• Make a check of Heater. If failure, reconnect wire and check again. If still wrong, replace Heater.
• Check whether the Washing Pump circuit is correct or not. If not, reconnect wire and check again. If still wrong, replace Washing Pump.
• Check whether the NTC circuit is correct or not. If not, reconnect wire and check again. If still wrong, replace NTC.

If the problem persists after all inspections, the PCB may be malfunctioning. Replace PCB and test again.

E4 Tree -> Inspection

E4: Overflow

• Is there any water on the bottom board?
  • No water: Make a check of Flooding Switch circuit. If failure, reconnect wire and check again. If still wrong, check if Flooding Switch is blocked or not. If blocked, repair or replace it.
  • Some water: Make sure consumer use proper detergent and rinse. If improper, give advice.
  • If OK: Make a check of Drain Hose. If kinked or blocked, solve the problem.
• Model with Pressure Switch: Check Pressure Switch circuit. If correct, proceed. If not, reconnect wire and check again. If still wrong, replace Pressure Switch.
• Model with Flowmeter: Check Flowmeter circuit. If correct, proceed. If not, reconnect wire and check again. If still wrong, replace Flowmeter.
• Maybe there is a real leakage: Find where leakage is and solve the problem as per service manual.

Do as follows: Remove side panels, drain water from the bottom board. Restart with a strong wash program. Observe the bottom tray for leaks. If no water appears after hours, stop the dishwasher with water and observe again after 1-2 hours.

E6 & E7 & Ed tree -> Inspection

• E6: Open-circuit failure of thermistor
  • Check whether the NTC circuit is correct or not. If not, reconnect wire and check again. If still wrong, replace NTC.
• E7: Short-circuit failure of thermistor
  • Check whether the NTC circuit is correct or not. If not, reconnect wire and check again. If still wrong, replace NTC.
• Ed: Communication failure
  • Between main control board and display board signal wire is loose? If NO, replace PCB assembly board. If YES, check connection.

Caution: Inspection trees are for reference only, as real situations can be unpredictable.

Troubleshooting Table Summary

The following tables provide common issues, possible reasons, analysis, operations, and remedies.

E1 Longer Inlet Time

E3 Heating Fault

E4 Overflow

E6 & E7 Open-circuit & Short-circuit

Poor Washing Performance

Noise