Question 1

How to disassemble the filter of the Kärcher BP 4 pump?

Accepted Answer

Here are the steps to disassemble the filter of your Kärcher BP 4 pump:

Unplug the device from the power outlet before any intervention
Unscrew the cover of the filling neck
Remove the pre-filter and the non-return valve to access the filtration elements
Clean with running water the removed elements to eliminate deposits and dirt
Reassemble correctly ensuring the proper mounting position (check the cutout of the pre-filter)

Maintenance tip: Regularly clean the pre-filter, especially if it is dirty, to maintain good flow and avoid pump operation issues.

Question 2

The BP 4 pump stops automatically after about a minute in auto mode, the A light flashes, and it needs to be restarted manually - how can I solve this problem?

Accepted Answer

This stop/restart cycle after one minute in automatic mode generally indicates that the pump is not drawing enough water. The auto mode has a protection feature that shuts off the device if it detects prolonged dry running, hence the flashing A light.

Check in this order:

Sufficient water level - Ensure that the water source (tank, well, basin) contains enough water. The pump's inlet must be submerged.
Clogged pre-filter - Remove and clean the pre-filter under running water. Deposits reduce flow and may trigger the protection system.
Intake hose - Check for any kinks, crushes, or blockages obstructing the inlet.
Check valve - Clean it also under running water. A dirty valve prevents proper priming.
Discharge leak - Inspect the entire discharge circuit (hose, fittings, outlet). A significant leak is enough to drop the pressure and restart the cycle.

Tip: After each cleaning, check that the pump can run for more than a minute before the next stop — that's a good sign. If the problem persists after addressing these points, consult Kärcher customer service.

Question 3

How to remove air from the Kärcher BP 4 pump and prime it correctly?

Accepted Answer

If your Kärcher BP 4 pump contains air, it will not be able to deliver properly. Here’s how to prime it:

Priming Procedure

Unscrew the filling neck cover on the pump body
Fill with water up to the edge of the tank
Screw the cover back on by hand until it stops (without forcing)
Open the pressure side shut-off valves
Set the switch to AUTO or I (On position)

Speeding Up Priming

To allow the air to escape more quickly, lift the discharge hose by about 1 meter and let the pump run. Wait for the water to flow evenly without air bubbles.

If the pump runs but still does not deliver

The problem may be due to a clogged filter or a stuck non-return valve. Clean the pre-filter and the non-return valve under running water. It is often residual air or deposits that block the passage.

Once priming is successful, the pump will operate normally and no warning lights should appear.

Question 4

Why does the red light blink after the BP 4 pump is turned off?

Accepted Answer

The blinking of the red light after the BP 4 pump is turned off indicates that the pump has detected a fault. This behavior is not normal and signals a problem that requires intervention.

What the red light means

On the BP 4 pump, the red light blinks to alert about:

Suction side (Light A): a water intake problem (air in the pump, clogged suction line, dirty pre-filter, insufficient flow, or dry run protection activated)
Discharge side (Light B): a water discharge problem (leak on the discharge line or on/off cycles due to pressure loss)

Diagnostic steps

To identify and resolve the problem:

Clean the pre-filter - this element clogs quickly and blocks the flow
Check the water source - ensure that the flow at the suction is sufficient
Inspect the hoses - look for cracks, leaks, or disconnections, particularly on the discharge line
Check the connections - all fittings must be airtight
Bleed the pump - residual air may remain after shutdown if priming was not complete

If the light remains on after these checks, consult the detailed troubleshooting table in the

Question 5

Why does my Kärcher BP 3 pump stop after 3 minutes?

Accepted Answer

The automatic shutdown of your Kärcher BP 3 pump after 3 minutes is a built-in dry running protection. This system protects the motor by detecting the absence of water or insufficient flow.

Main causes

Not enough water at the suction - The tank, well, or cistern is not supplying the pump properly
Clogged suction filter - A dirty filter reduces the flow below the minimum (approximately 60 l/h)
Air entry into the circuit - A leak in the suction line or poor priming prevents water from arriving
Improperly positioned suction line - The water intake is not submerged enough or is not sucking properly

Solutions to check

Ensure that your water source has a sufficient amount
Check all seals and suction hoses for leaks
Clean the suction filter if it is clogged
Properly prime the pump - Unscrew the top filling cap, fill with water to the edge, then screw the cap back on. This is the most often forgotten step
Position the water intake deep enough in the tank

Test again after these checks. If the shutdown persists, there is really a lack of water at the pump's intake.

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