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Step by step guide

Evolution V4: Replace switch box

Servicing our pressure washers are quite straight forward and could be done by most people by following the step-by-step instructions in this manual. Please go trough the whole manual before starting work on your pressure washer to make sure you understand the procedure and that you have the necessary tools to complete the task.

Always unplug the pressure washer from both the mains power and the water outlet before starting the service. Even though power and water is disconnected there may be pressurized water in the hose. Discharge this pressure by pulling the trigger on the gun. Make sure your work area is clean and appropriate for the work you are about to do. There will usually be a small amount of water inside the pump and hose. If you are doing a 10-year service, then be prepared to collect the used oil from the oil chamber. Please dispose of the oil in accordance with local law and regulations. ISO 46 hydraulic oil can be substituted with similar non detergent oil of the same viscosity.

00. Parts and tools

An overview of what is needed to do this service.

01. Remove water filter

Remove water filter by unscrewing it counterclockwise.

02. Remove the hose reel

Release the short pressure hose from the pump outlet. Unscrew the 3 T25 screws from the back cabinet. Take off the cover and the hose reel.

03. Remove screws from the back cabinet

Remove the power cable from the cable reel so you can access the two screws behind the reel. Unscrew the 11 T25 screws from the backside of the pressure washer.

04. Lift off the rear cabinet

Put the pressure washer face down. Lift off the rear cabinet. Release the strain reliever and the power cord.

05. Remove screws from the pump.

Unscrew the 3 T25 screws securing the motor/pump.

06. Remove the motor/pump

Carefully lift the motor/pump out of the front cover. Turn it 180° before placing it on a flat surface. Remove the on/off button, its extension and the pump head cover.

07. Disconnect motor power cords

Release the two spade connectors from the motor power cord. Press the small tab indicated in the picture then gently pull them apart.

08. Disconnect earth cable

Release the motor earth cable by unscrewing the small Phillips head screw securing it.


09. Remove switch box

Remove the switch box by pulling it in the direction indicated. It is press fitted onto the start/stop valve on the pump.

10. Open the old switch box

Unscrew the 5 Phillips head screws that secures the switch box cover and remove the cover.

If your switch box includes the mains power cord, you can jump straight to step 17.

11. Extract switch/cord assembly

Remove both the micro switch, the main switch and the whole cord assembly from the old switch box.

We will be reusing the mains power cord connected to the main switch.

12. Extract the mains power cord

Remove the mains power cord by releasing the two spade connectors from the main power switch. Push down the locking tab on the connector and pull gently to release the cord. Now its time to move the mains power cord to the new switch box assembly.

13. Fit the switch/cord assembly to the new switch box

Fit these two spade connectors to the main switch. They can be connected in any order since this is alternating current.

Place the whole cord and switch assembly back into the new switch box. Align the holes in the micro switch with the corresponding protrusions in the switch box cover.

14. Check positioning of the different parts

Make sure that the main switch is properly seated in its corresponding slot.

Also check that the small O-ring, the sliders, the spring and the main switch shaft is present and properly positioned.

15. Close the new switch box

When you are satisfied with the placement of both cabling and switches, put the switch box lid back on.

Secure the lid using 5 Phillips screws.

16. Test the switches

Test that the main switch is fully operational by twisting the shaft clockwise and counterclockwise.

There should be an audible click sound as the main switch engages and disengages.

Test the microswitch in a similar fashion by using a thin nail or screwdriver to push on the small slider in the direction of the arrow. There should be an audible click when engaged and a similar click when disengaged.

If any of the switches fails to make a clicking sound, open the switch box to investigate further.

17. Reattach the switch box

Attach the switch box to the pump. You need to use a decent amount of force to get the box firmly seated on the start/stop valve. It should pop into place.

18. Connect the motor power cord

Reattach the two spade connectors from the switch box to the motor. Give them a light tug to check that they are securely locked.

19. Attach earth cable

Attach the earth cable to the motor. Secure it using a Phillips head screw.

20. Reattach the on/off button

Reattach the on/off button, its extension and the pump head cover.

21. Place the motor/pump unit back into the front cover

Carefully lift the motor/pump and turn it 180° before placing it into the front cover.

Make sure the on/off button and its extension are properly positioned so that they can operate freely.

22. Secure motor/pump unit to the front cover

Secure the motor/pump and the switch box using the 3 T25 screws.

23. Fit the back cabinet

Fit the strain reliever and make sure the power cord is correctly situated.

Place the back cabinet onto the front cover. Adjust so both parts align correctly. If you are having trouble to get a good fit, check that the power cables and motor cowling are aligned correctly.

24. Secure the back cabinet

Once you are happy with the alignment of the back cabinet, secure the front cover to the back cabinet with 11 T25 screws.

25. Fit the hose reel assembly

Fit the hose reel assembly to the back cabinet.

Push the interconnect pressure hose into the depression.

Fit the cover and secure it with 3 T25 screws.

Connect the hose to the outlet.

26. Reattach the water filter

Check that the filter cassette is clean and without damage.

Reattach the water filter to the water inlet.

27. First start after service

Congratulations with finishing the service of your AVA product.

It is now time to do the first start after service.


  1. Start by connecting the pressure gun to the hose.
  2. Connect water.Make sure no water is leaking from the inside or anywhere else on the pressure washer.
  3. Pull the trigger and let the water flow until there is no more air coming out.
  4. Connect the power cord.
  5. Turn on the pressure washer.
  6. Pull the trigger and let water run for a minute before connecting a nozzle.
  7. Connect the nozzle.
  8. Use the pressure washer and make sure it is operating as normal.

28. Troubleshooting

Water is leaking from the inside

  • Disconnect the power and open the pressure washer to locate the leak.
  • Take necessary action to remedy any leaks.

Motor runs and won't stop when you release the trigger

  • This is most likely due to an improper seating of the switch box on the start/stop valve.
  • Open the machine and check that the switch box is correctly seated.

The pressure washer won't turn on

  • Check that the power cable is connected.•Check that the circuit breaker has not been tripped.
  • Check that the fuse in the power plug is intact (UK models only).
  • Open the machine and check that all the internal cabling is connected.

Poor performance/pressure

  • Improper assembly or dirt/debris in the pump.
  • Check that the pump and especially the main valve for foreign objects/debris.
  • Make sure that the spring in the main valve is correctly seated and working as intended.

Motor is making a humming noise and is not able to start

  • Check that the capacitor is connected to the motor.
  • It should be connected with one white and one black cable.