Dealing with Karcher on/off switch problems? If your Karcher pressure washer simply won't turn on, this means the on/off switch isn't working properly and needs to be replaced. That's why we're here to help!
In this article, written by an in-house eSpares repair expert, we explain how to fix this problem. The Karcher switch comes as part of the electrical assembly inside your pressure washer, so you will need to replace this entire assembly to get your Karcher pressure washer working properly again. Let's take a look...
How do you know your Karcher pressure washer's on/off switch needs replacing?
- As mentioned above, you will know you need to replace the internal electrical assembly (which includes the on/off switch) if your Karcher is not switching on when you turn the switch.
What you will need
To replace a Karcher electrical assembly with the on/off switch, you will need the following...
- Small flatblade screwdriver
- Pin nose pliers
- Torx T15 screwdriver
- Torx T20 screwdriver
- H6 socket or a Torx T40 screwdriver (either one will work)
- Karcher on/off switch (part of the electrical assembly)
When buying a new electrical assembly for your Karcher pressure washer, remember to make sure you get the correct one for your particular make and model of appliance. If you're not sure what make or model your appliance is, our model number finder page is here to help!
Safety Advice
Remember, always make sure an appliance is switched off and unplugged from the mains (if applicable) before carrying out any work.
Also, please note that we're using a Karcher K4 model for this guide. If you own a different model of Karcher pressure washer, there's a chance that this process may differ slightly.
Replacing the on/off switch on a Karcher pressure washer step-by-step
Let's start! To learn how to replace a Karcher on/off switch and electrical assembly, either follow the video guide below or read our written tutorial beneath.
In the video above, one of our presenters walks you through this repair step-by-step, showing you everything you need to do to get your appliance back in action.
Step 1 - Unscrew the water inlet hose connection
First, you will need to unscrew and remove the small black water inlet hose connection. This is located at the bottom of the front of the casing, as pictured below.
Step 2 - Remove the eight casing screws
Next, using your Torx T15 screwdriver, you will need to unscrew the eight screws that keep the front casing connected. Of these eight screws, six are located at the back of the pressure washer, with three on either side (leading down from just below the top handle to just above the wheels).
With these six screws removed, you will then need to unscrew the last two screws from the underside of the pressure washer (one on either side between the Karcher wheels).
Step 3 - Remove the tool carrier
Next, you will need to remove the tool carrier. To do this, remove the two small black lugs that are located on the underside of the pressure washer. These lugs hold the tool carrier in place.
First, use your small flatblade screwdriver to carefully pry each lug out a little bit. You won't be able to use the screwdriver to fully remove the lugs - you just need to wedge the screwdriver blade underneath and loosen them enough to be able to grip the circular end with your pin nose pliers.
Then, once the lugs have been pulled out a little, use your pin nose pliers to work the lugs all the way out. The lugs will be quite stiff, so take your time and be careful not to damage them with your pliers as you remove them.
With the two lugs removed, you will be able to remove the tool carrier.
Step 4 - Fully disconnect the front casing
After removing the eight screws earlier, you will now be able to lift the front casing a little way off the pressure washer. Holding the casing on either side, carefully wiggle it free of the water inlet valve inside, and lift it up a little.
You won't be able to fully lift the casing as it will still be connected on the inside by the Karcher soap dispenser hose and the mains cable. To fully free the casing, first reach inside and pull the soap dispenser hose out of its inner clip.
Then also remove the mains cable from the inner clip that holds it in place.
Now, returning to the soap dispenser hose, you will need to pull off the end that's connected to the small soap feed pipe. This is the pipe that's on the pump housing, at the top of the motor inside the pressure washer.
Step 5 - Remove the control knob
You will now be able to lift away the front casing. At this stage, it's time to remove the Karcher control knob from the casing. To do this, just squeeze in the three small black clips that keep the knob held into place...
Then pull the control knob out of the front of the casing.
Step 6 - Remove the motor
Now it's time to remove the Karcher motor. At this point, it's a good idea to wear some safety gloves if you have any.
To disconnect the motor, first remove the motor retaining clip from the top of the motor. To do this, slot your flatblade screwdriver behind the clip and pry it free.
Once you've pried the clip out enough, you should be able to grab hold of it and finish pulling it out by hand.
Now you can go ahead and remove the motor. You will need a second person to help you do this. With one person firmly holding the pressure washer's main body, the other person will need to grab hold of the motor and work it off the pump housing (which is where the motor is connected at the top).
Once worked off the pump housing, the motor can be removed and stood upright.
Step 7 - Separate the pump assembly from the motor
You now need to separate the pump assembly from the top of the motor. Using a H6 socket (or a Torx T40 screwdriver if you don’t have a H6 socket), you will need to remove the four bolts from the metal pump cover. Make sure you keep the motor upright when you do this to prevent oil or water from leaking out.
When unscrewing these bolts, you're going to want to unscrew each one bit by bit. This means making rounds where you gradually loosen each bolt, repeatedly moving from one bolt to the next, instead of fully unscrewing each bolt one at a time. Otherwise, if you fully remove one bolt before moving onto the next, it will make the others tighter and more difficult to unscrew.
Once unscrewed, you will be able to separate the pump assembly from the top of the motor.
Step 8 - Remove the electrical assembly from the motor
Now it's time to remove the Karcher electrical assembly from the motor. To do this, use your Torx T20 screwdriver to unscrew the earth screw (indicated below) that connects the main earth wire to the motor.
Then, to fully disconnect the electrical assembly from the motor, simply disconnect the mains connection plug.
When you disconnect this plug, a small black gasket will fall off the assembly - it may still be on the two motor pins (as pictured below) or it may fall off entirely (also pictured below). Make sure you keep this at hand and don't lose it or throw it away, as you will need to refit it later.
Step 9 - Fit the new electrical assembly onto the motor
Once you have your new Karcher electrical assembly, it's time to connect it onto the motor. Start by reconnecting the mains connection plug. This needs to refit correctly so let's take a closer look. On the part of the plug coming from the motor, you will be able to see a slot (two ridges) on one side of the plug...
And you will also be able to see a groove (one ridge) on the other side of the plug.
Now let's look at the plug on the electrical assembly. On the inside of the plug, you will be able to see the same thing. There will be a groove (one ridge) on one side inside the plug...
And a slot (two ridges) on the other side inside the plug.
When refitting the plug, make sure the slot and the grooves refit into the opposite sides, so that a groove fits inside a slot and vice versa.
Next, you will need to make sure you refit the small black gasket that came off the old electrical assembly earlier. To do this, simply slot the gasket into place on the new assembly, ensuring the flat side of the gasket is closest to the assembly's long plug.
Now you can fit the new electrical assembly onto the top of the motor. When doing this, slot the plug into the side of the motor, making sure you hold the small black gasket in place so it doesn't fall off.
As mentioned above, you need to make sure the small black gasket doesn't fall off again and stays in the correct position. It will need to remain connected to the assembly and slot over the two location pins on the motor.
Step 10 - Refit the pump assembly onto the motor
Now it's time to refit the pump assembly onto the top of the motor. With one hand, hold the electrical assembly in place, as pictured below...
And slot the pump on top of the motor.
When you do this, make sure the black water feed pipe on the side is lined up with the motor opening beneath it.
Then, using either a H6 socket or Torx T40 screwdriver, screw the four screws back into place to secure the pump assembly onto the motor. Again, when doing this, make sure you only tighten each bolt little by little, repeatedly moving around from one bolt to the next, again and again. This will take a bit of time, but if you screw one bolt all the way in before moving onto the others, it will make this process a lot more difficult. Don't stop this process until all four bolts are firmly tightened.
Now, using your Torx T20 screwdriver, screw the earth wire back onto the motor.
Step 11 - Fit the motor back into the pressure washer
With the pump assembly fitted onto the motor, you can now refit the motor unit back into the pressure washer. Again, you will need a second person to help you do this. With one person holding the pressure washer, the other person will need to work the motor and pump onto the pump housing at the top.
Then slot the metal clip back into place on the pump housing above the motor. This clip will keep the motor and pump securely connected to the pump housing.
Step 12 - Reconnect the front casing from inside
Now you can begin reconnecting the front casing, starting by refitting the soap dispenser hose and mains cable inside. First, reattach the end of the soap dispenser hose onto the small soap feed pipe above the motor.
Then reconnect the mains cable to its clip inside the casing.
You can then go back to the soap dispenser hose and clip it back onto the small inner clip.
Step 13 - Refit the front casing onto the pressure washer
You can now slot the front casing onto the pressure washer. There are a few things to note when you do this. First, make sure that the two black tabs at the bottom of the pressure washer go outside the casing. Otherwise, if they're inside, the casing just won't fit properly.
Also, on one side, you will need to align the mains cable with the indent on the side of the pressure washer (as pictured below) to ensure it doesn't get trapped between the casing and the pressure washer...
And, on the other side, you will also need to align the water outlet with the hole there for the same reason.
With all this accounted for, you will be able to slot the front casing into place on the pressure washer.
Step 14 - Screw the casing into place
With the casing in place, secure it by refitting the eight screws you removed earlier using your Torx T15 screwdriver. These are the six screws at the back...
And the two screws on the underside of the pressure washer.
Step 15 - Refit the tool carrier
Now you can refit the tool carrier. First, slot the carrier into place on the front of the pressure washer at the bottom.
Then push the two black lugs back into place at the bottom of the pressure washer. Make sure you align the flat sides of the lug circles with the black ridges on either side of the openings, ensuring they can slot all the way into place.
Step 16 - Refit the control knob
Next, you can refit the control knob. You will be able to see the control switch through the control knob opening.
Make sure this is lined up with the slot on the inside of the control knob.
With this lined up, you can simply push the control knob back into place in the opening over the control switch.
Step 17 - Refit the water inlet connection
Finally, screw the small black water inlet hose connection into place at the bottom of the front of the pressure washer. Once you've done this, your pressure washer will be fully reassembled with the new electrical assembly and switch fitted inside!
How to find the right on/off switch for your Karcher pressure washer at eSpares
Replacing your pressure washer's electrical assembly (with the on/off switch included) will get your appliance back in working order - and by doing it yourself, you'll save plenty of money by avoiding calling a costly repair professional or buying a whole new appliance when you don't need to.
Don't forget, you can find the part you need right here in our range of Karcher motors, which includes new electrical assemblies. Plus, we're here to help if you need any further guidance with choosing the exact part you're looking for.
Does your Karcher pressure washer have everything it needs?
Once you've got your pressure washer fixed, it's a good idea to make sure you've got everything you need to keep on cleaning efficiently. Here at eSpares, we have a wide range of pressure washer cleaning detergents to help you get the best from your appliance, no matter what surface or outdoor area you need to clean.
Finally, don't forget that we're also here to help you fix any other problems that might arise with your pressure washer. Not only do we have plenty of pressure washer repair guides to help you fix common problems, but we also have a huge range of pressure washer parts and accessories to help you get the job done quickly and affordably. It's easy with eSpares!
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