Technical Service Manual - Dishwasher

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 -> Function Description

This section describes the water circuit scheme and processes.

Water circuit scheme

Diagram Description: A schematic illustrates the water flow within the dishwasher. It shows the inlet water route (magenta), drain water route (blue), and cycle water route (cyan). Key components include the inlet hose, air breaker, water softener, top sprayer arm, upper sprayer arm, lower sprayer arm, sump, inlet valve, washing pump, and drain hose leading to the drain pump.

Note: This page is for models with common inlet hose.

Diagram Description (Alternative): A similar schematic for models with an aquastop hose, showing inlet water route (magenta), drain water route (blue), and cycle water route (cyan). Components include inlet hose, air breaker, water softener, top sprayer arm, upper sprayer arm, lower sprayer arm, sump, inlet valve (involved in aquastop hose), washing pump, and drain hose to the drain pump.

Note: This page is for models with aquastop hose.

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 enters through the main water route, is softened by the softener, and then enters 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 working washing pump, then through the spray arm nozzles, over the dishes, into the sump, and back to the washing pump for the next water cycle.

Location -> Theory of parts

Diagram Description:

An exploded view diagram shows the internal layout of the dishwasher, indicating the locations of key components: Inlet valve, Washing Pump, Heater, Main PCB, Drain Pump, and Softener.

Note: Exploded view and part list may differ slightly between models. Refer to the newest vision provided by Midea.

PCB -> Theory of parts

PCB Description:

The Printed Circuit Board (PCB) serves as the control center of the dishwasher, receiving and processing signals from components, sending commands, and managing feedback information.

Access PCB

The PCB can be accessed by removing a protecting box located at the bottom of the machine. The steps involve:

1. Disconnect power supply.
2. Remove the 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 connectors from the PCB.
6. Remove the PCB.
7. Reverse the above procedure for installation.

Diagram Description:

A view of the bottom of the machine showing the location of the 'Protecting Box'.

View of PCB

A detailed diagram of the PCB layout is provided, showing various components and their markings.

Note: This map applies to the 7601S model.

Description of PCB Components

Minor differences in component placement may exist between models, but the markings on the PCB retain the same meaning.

Inlet Valve -> Theory of parts

Location of inlet valve

Diagram Description: A bottom view of the dishwasher showing the location of the inlet valve.

Appearance

Diagram Description: An illustration of the inlet valve, showing its terminals, connection to the air breaker, connection to the inlet water hose, and the electric coil inside.

The work principle

The inlet valve is an electromagnetic valve that controls water entry. It is normally closed. When water is required, the controller sends an electric signal to the coils, opening the valve. The valve consists of an electric coil, valve body, valve pole, and filter.

The defeat point

1. Valve coil broken: Prevents the valve from opening, causing an E1 error.
2. Filter jammed: Blocks water entry, causing an E1 error.
3. Loose connector: Prevents the valve from opening, causing an E1 error.
4. Valve pole rusted or blocked by debris: Prevents the valve from opening or closing, causing an E1 or E4 error.

Technical data

Access inlet valve

Steps to access the inlet valve:

1. Disconnect power.
2. Remove the water inlet hose (caution: be careful of residual water).
3. Remove the cover of the bottom board.
4. Disconnect the 2 terminal lugs from the inlet valve.
5. Pull out the valve slightly, then contrarotate it to remove.
6. Remove the clamp and disconnect the inlet hose (to air breaker) from the water valve.
7. Reverse the above procedures to install.

Diagram Description:

Images show the bottom view of the dishwasher with the inlet valve location, and a close-up of the clamp and locking terminals.

Inspect inlet valve

Check electric part

1. Open the protecting box and take out the PCB.
2. With the door closed, unplug CON3 and ACN wires. Use a multimeter to measure resistance between the blue wire (EV1) and the blue wire (ACN). The normal resistance is approximately 4.4kΩ to 4.8kΩ.
3. If the measured resistance is incorrect, the valve coil may be broken or the connector loose. Check the connection first. If the issue persists, replace the valve.
4. If the resistance is OK, inspect the valve body.

Check machine part

1. If the electric part is OK, check the machine part.
2. Check the valve filter. If blocked, clear residues.
3. If the filter is clear but water does not enter, check if the valve operates. If not, replace the valve.
4. If water continuously enters, replace the valve.

Diagram Description:

Images show the PCB with EV1 and ACN connectors highlighted, and a bottom view of the dishwasher indicating the inlet valve location.

Drain Pump -> Theory of parts

Location of Drain Pump

Diagram Description: A bottom view of the dishwasher showing the location of the drain pump.

The work principle

The drain pump consists of an electrical motor, impeller, inlet, and outlet. It is driven by a permanent magnet synchronous motor with a rotor made of permanent magnet material. The stator comprises silicon steel stack and coils. The rotor starts easily when power is applied.

The defeat point

1. Motor coil broken: Prevents the pump from working, causing an E1 error.
2. Weak motor rotor magnetism: Prevents the pump from working, causing an E1 error.
3. Loose connector: Prevents the pump from working, causing an E1 error.
4. Rotor locked by residues: Prevents the pump from working, causing an E1 error.
5. Loose drain pump assembly rack: Causes noise.
6. Bad non-return valve: Results in excessive residual water.

Explanatory notes: A drain pump failure can lead to an E1 error. If water is not drained, the pressure switch may cut off the inlet valve, preventing water entry and triggering the E1 error.

Technical data

Access drain pump

Steps to access the drain pump:

1. Drain water from the dishwasher and disconnect the power supply. (Ensure no water remains to avoid wetting the floor.)
2. Remove the cover of the bottom board (loosen top hooks first, then left/right hooks; be careful not to break hooks).
3. Label and disconnect the two terminal lugs from the drain pump.
4. Contrarotate the drain pump to remove it.
5. Reverse the above procedures to install.

Diagram Description:

A bottom view of the dishwasher indicating the drain pump location.

Inspect drain pump

Check the electric part

1. Open the protecting box and take out the PCB.
2. With the door closed, unplug CON3 and ACN wires. Use a multimeter to measure resistance between the red wire (PS) and blue wire (ACN). Normal resistance is about 220Ω to 250Ω.
3. If the measured resistance is incorrect, the pump coil may be broken or the connector loose. Check the connection first. If the issue persists, replace the drain pump.
4. If resistance is OK but the pump doesn't work, the magnetism may be too weak. Replace the drain pump.

Check the machine part

1. If the electric part is OK, check the machine part.
2. Remove the bottom board.
3. If the non-return valve is wrongly assembled, residual water will remain. Re-assemble the non-return valve.
4. If the drain pump works but drains little or no water, check the drain hose or drain body.

Diagram Description:

Images show the bottom view of the dishwasher with the drain pump location, and the PCB with PS, ACN, and CON1 connectors highlighted.

Heater -> Theory of parts

Location of Heater

Diagram Description: A bottom view of the dishwasher showing the location of the heater.

The work principle

Diagram Description: A simple circuit diagram showing a heater connected in series with a fuse and a pressure switch.

Technical data

The defeat point

1. Heater coil broken: Prevents the heater from working, causing an E3 error.
2. Fuse is active: Prevents the heater from working, causing an E3 error.
3. Loose connector: Prevents the heater from working, causing an E3 error.

Access heater

Steps to access the heater:

1. Drain off water and disconnect power. (Ensure no water remains.)
2. Remove the bottom board.
3. Label and disconnect the terminals.
4. Remove the 2 clamps fixing the pump hoses. (Caution: Clamps are easily damaged and cannot be reused; replace with a new universal clamp.)
5. Contrarotate the upper pump to remove it.
6. Reverse the above procedures to install.

Diagram Description:

Images show the heater assembly with clamps and terminals, and a close-up of the heater element.

Inspect heater

1. Remove the bottom board.
2. Use a multimeter to measure resistance between the two terminals. Normal resistance is about 27Ω to 30Ω.
3. If the resistance is incorrect, the heater coil or thermostat may be broken. Replace the heating element or thermostat.

Washing Pump -> Theory of parts

Location of Washing Pump

Diagram Description: A bottom view of the dishwasher showing the location of the washing pump.

The work principle

Diagram Description: A schematic of the washing pump motor, showing connections for the main coil (M-main coil) and assistant coil (A-assistant coil), with temperature indication (150°C).

The washing pump is an asynchronous motor with a capacitor. The stator consists of silicon steel stack and two coils: a main coil and an assistant coil.

The defeat point

1. Motor coil broken: Prevents the wash pump from working, causing an E3 error.
2. Weak motor rotor capacitor: Prevents the washing pump from starting, potentially causing electromagnetism noise. If power continues, the thermal protector may engage, causing an E3 error.
3. Loose connector: Prevents the wash pump from working, causing an E3 error.
4. Rotor locked by residues: Prevents the wash pump from working, causing an E3 error.
5. Loose drain pump assembly bracket: Causes noise.
6. Machine unused for a long time: May prevent the wash pump from starting.

Technical data

Access Washing Pump

Steps to access the washing pump:

1. Disconnect power.
2. Remove bottom board.
3. Label and disconnect the terminals.
4. Remove the 2 clamps for fixing the pump hoses. (Caution: Clamps are easily damaged and cannot be reused; replace with a new universal clamp.)
5. Contrarotate the upper pump to remove it.
6. Remove the 1 screw fixing the impeller to the pump.
7. Remove the 2 screws fixing the lower pump to the motor.
8. Reverse the above procedures to install.

Diagram Description:

Images show the impeller, lower pump, screw connections, and the ML-L, ML-H, ACN connectors on the PCB.

Inspect Washing Pump

Check the electric part

1. Open the control panel and take out the PCB.
2. With the door closed, unplug CON1 and CON2. Use a multimeter to test resistance between wires (ML-H and ACN) and (ML-H and ML-L). Normal resistance is about 100Ω to 130Ω for ML-H/ACN, and 35Ω to 45Ω for ML-H/ML-L.
3. If resistances are incorrect, the pump coil may be broken or the connector loose. Check the connection first. If the issue persists, replace the washing pump.
4. If resistance is OK but the pump doesn't work, the capacitor may be weak. Replace the capacitor.

Check the machine part

1. If the electric part is OK, check the machine part.
2. Remove the bottom board.
3. Check the pump assembly. If the bracket is loose, tighten it to prevent noise.
4. If the wash pump cannot start and the machine has been unused for a long time, the seal element may be bonded.
5. If the drain pump works but drains little or no water, check the vane wheel.

NTC -> Theory of parts

Location of NTC

Diagram Description: A bottom view of the dishwasher showing the location of the NTC (Negative Temperature Coefficient Thermistor) integrated into the sump.

The work principle

The NTC thermistor is integrated into the sump and is used to measure the temperature of the water in the tub.

Access NTC

Steps to access the NTC:

1. Remove the bottom board.
2. Remove two screws securing the NTC to the sump.
3. Take out the NTC.
4. Reverse the above procedure to install.

Inspect NTC

1. Open the protecting box and take out the PCB.
2. With the door closed, unplug the RE connector. Use a multimeter to test resistance between the two blue wires (RE and GND). The normal resistance is shown in the table below.
3. If the resistance is incorrect, there is a problem with the NTC circuit. Check the connection first. If the issue persists, replace the NTC.

NTC resistance table

Diagram Description:

An image shows the PCB with the RE and GND connectors highlighted.

Flowmeter -> Theory of parts

Location of Flowmeter

Diagram Description: A bottom view of the dishwasher showing the location of the flowmeter, integrated into the Air Breaker.

The work principle

The flowmeter is integrated into the Air Breaker and measures the amount of water that has entered the appliance. It consists of an impeller, tongue tube, and terminal. When water passes through, it rotates a magnetic impeller. The tongue tube senses the impeller's magnetic field and sends electronic pulses.

Diagram Description:

An illustration showing the flowmeter and its impeller.

Access Flowmeter

Steps to access the flowmeter:

1. Remove the baseboard, top panel, and left side panel.
2. Remove the plastic nut inside the tub that secures the air breaker to the tub (replace the air breaker if the 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 the above procedure to install.

Inspect Flowmeter

1. Open the protecting box and take out the PCB.
2. With the door closed, unplug the CON2 wire. Use a multimeter's diode setting to test between the black wire (FM) and blue wire (GND) to confirm if electrical pulses are sent out while water passes through the flowmeter.
3. If there are continuous electrical pulses, the multimeter will emit a continuous sound.
4. If there are no electrical pulses, the multimeter will not send sound. This indicates a problem with the flowmeter circuit. Check the connection first. If the issue persists, replace the air breaker.

Diagram Description:

An image shows the PCB with the FM and GND connectors highlighted.

Safety hose -> Theory of parts

Location of Safety Hose

Diagram Description: A bottom view of the dishwasher showing the location of the safety hose.

The work principle

There are two types of Safety Hoses: Mechanical Aquastop Hose and Electronic Aquastop Hose.

Mechanical Aquastop Hose

Diagram Description: Images show a two-layer hose and foaming material inside.

This hose has two layers. If a water leak occurs, air space between the layers fills with water. The foaming material expands, locking the hose. This may trigger an E1 alarm.

Electronic Aquastop Hose

Diagram Description: Images show a two-layer hose, an electromagnetism valve inside, and a connection to the air breaker.

This hose also has two layers. If a water leak occurs and water flows onto the bottom tray, a flooding pressure switch activates the electromagnetic valve on the hose, cutting off the water supply. The machine will then set off an E4 alarm.

Access Safety Hose

Steps to access the safety hose:

1. Remove the baseboard, side baseboard, top panel, and left side panel.
2. Remove the clamp, cut the bound belt, and disconnect the wire connector. Then, the inlet hose can be pulled out.
3. Reverse the above procedure to assemble.

Diagram Description:

Images show the clamp and hose connections during access.

Inspect Safety Hose

Electronic Aquastop Hose

1. Open the protecting box and take out the PCB.
2. With the door closed, unplug the CON3 and ACN wires. Use a multimeter to measure resistance between the blue wire (EV1) and blue wire (ACN). Open circuit and short circuit are both incorrect.
3. If the measured resistance is incorrect, the valve coil may be broken or the connector loose. Check the connection first. If the issue persists, replace the safety hose.

Mechanical Aquastop Hose

Moisture absorption by the foaming material in the mechanical device can cause a self-lock fault (preventing water filling), which is non-resettable.

Test Program

How to activate Test Program

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

Test Program Operation Table

Error Codes during Test Program: E1, E3, E4, E6, E7, E8, Ed.

To activate the test program: with the door open and within 60 seconds after power-on, hold down the Start/Pause button and press the POWER button until the machine enters Test Program. The appliance will pause and stand by (step 00). Then, close the door to start the Test Program.

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

Notes:

1. The method to activate the test program may vary slightly between different models.
2. Switch off the unit from the wall, then switch it on again before following the instructions above to activate the test cycle.

Procedure -> Test Program

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

Error Code -> Test program

How to know which error code has occurred

Refer to the 'Test Program Operation' table to identify error codes. For example, if error 1 occurs, the buzzer will alarm for 30 seconds and 'E1' will be displayed. Other error alarms follow the same pattern.

The relationship between indicator combinations and error codes is shown in the figure (not provided here). Most models follow this regulation.

Attention

Priority level of E4 is the highest. E4 operation is valid only after other error operations have completed. Once E4 operation is done, all other errors become invalid.

In test program, E1, E3, E4, E6, E7, E8, Ed are valid error codes.

How does the appliance react when error code occurred

E1 Water filling exceed pre-set time

If the inlet valve opens for 4 minutes but the water quantity is insufficient (measured by pulses), E1 occurs. When E1 occurs, the drain pump runs until the flowmeter is motionless for 2 minutes, and all other components stop. The buzzer alarms for 30 seconds, and error 1 is shown.

E3 Heating exceed pre-set time

If the heating element works for 60 minutes but the water temperature detected by NTC has not reached the desired value, E3 occurs. When E3 occurs, the drain pump runs until the flowmeter is motionless for 2 minutes, and all other components stop. The buzzer alarms for 30 seconds, and error 3 is shown.

E4 Overflow

If the overflow micro-switch activates for longer than 2 seconds, E4 occurs. When E4 occurs, the drain pump runs until the flowmeter is motionless for 2 minutes, and all other components stop. The buzzer alarms for 30 seconds, and error 4 is shown.

Note: Priority level of E4 is the highest. E4 operation is valid after other error operations have done. When E4 operation is done, all others are invalid.

E6 Open-circuit failure of thermistor

In test program, if an open-circuit failure of the thermistor is detected, E6 occurs. When E6 occurs, the drain pump runs until the flowmeter is motionless for 2 minutes, and all other components stop. The buzzer alarms for 30 seconds, and error 6 is shown.

E7 Short-circuit failure of thermistor

In test program, if a short-circuit failure of the thermistor is detected, E7 occurs. When E7 occurs, the drain pump runs until the flowmeter is motionless for 2 minutes, and all other components stop. The buzzer alarms for 30 seconds, and error 7 is shown.

Ed Communication failure

If communication data anomalies are detected on the display board for 20 seconds, Ed occurs. Check display board connections, reinsert the connecting line, and power on again.

E8 Diverter valve fault

(For models equipped with a diverter for alternative washing function)

During the test program, if the machine does not detect the diverter valve signal for 15 seconds or the diverter valve positioning for 60 seconds, E8 occurs. During the washing program, if the diverter valve signal is not detected for 15 seconds or positioning is not accurate for 60 seconds, the diverter valve will stop, and E8 will be set off after the washing program ends.

When E8 occurs, the drain pump runs until the flowmeter is motionless for 2 minutes, and all other components stop. The buzzer alarms for 30 seconds, and the error code is shown.

Inspection Trees

E1 code tree -> Inspection

Flowchart Summary: Checks for water in the tub. If no water, checks inlet hose (Aquastop). If little water, checks tap. If water enters but slowly, checks inlet hose for blockage. If OK, checks inlet valve circuit. If model has flowmeter, checks flowmeter circuit. If model has pressure switch, checks pressure switch circuit. If still issues, checks drain hose and pressure switch (140/120). If problems persist, suggests PCB malfunction.

E3 tree -> Inspection

Flowchart Summary: Checks water temperature. If high, checks for over-heat proof switch. If low, checks filter for jamming. If OK, checks heater circuit. If OK, checks washing pump circuit. If OK, checks NTC circuit. If issues persist, suggests replacing the respective component (switch, filter, heater, washing pump, NTC).

E4 tree -> Inspection

Flowchart Summary: Checks for water on the bottom board. If some water, checks flooding switch circuit. If no water, checks drain hose. If OK, checks flowmeter circuit (if applicable) or pressure switch circuit (if applicable). If issues persist, suggests checking for real leakage or replacing components (flowmeter, pressure switch). Also provides general advice on loading dishes and checking the appliance level.

E6&E7&E8&Ed tree -> Inspection

Flowchart Summary:

• E6 (Open-circuit failure of thermistor): Checks NTC circuit. If OK, checks flowmeter circuit. If OK, suggests replacing NTC.
• E7 (Short-circuit failure of thermistor): Checks NTC circuit. If OK, checks flowmeter circuit. If OK, suggests replacing NTC.
• E8 (Distributary valve fault): Checks distributary valve circuit. If OK, checks flowmeter circuit. If OK, suggests replacing the valve.
• Ed (Communication failure): Checks if the signal wire between main control board and display board is loose. If loose, correct connection. If OK, suggests replacing the PCB assembly board.

Caution: Inspection trees are for reference only due to unpredictable real situations.

Troubleshooting

E1: Longer inlet time

E3: Heating fault

E4: overflow

E6 & E7: open-circuit & short-circuit

Poor drying performance

Noise