Bosch won't drain on programmes

Hi. On Bosch machines, E18 is usually a drain/pump-out problem, but the fact it will drain on a drain-only cycle is a very useful clue. It suggests the pump can work, so the fault may be intermittent or related to how the control is deciding to drain during wash programmes.

Before checking anything internal, isolate the washing machine from the mains.

1. Check the drain hose installation Make sure the hose isn’t pushed too far down the standpipe or connected in a way that could cause siphoning or poor flow. Also check for a partial blockage where the hose bends at the back of the machine.

2. Inspect pump operation during a failed programme When it should be draining on a wash cycle, listen carefully. - If the pump hums but water doesn’t move, there may still be a restriction or a weak pump. - If the pump doesn’t run at all on the programme, the issue is more likely control-related or sensing-related.

3. Check for an intermittent pump fault A pump can pass a drain-only test but fail when hot or under repeated use. Check the impeller for looseness or stiffness. If it feels worn or sloppy, the pump may be failing intermittently.

4. Check the pressure system A partially blocked pressure chamber or pressure switch hose can confuse the control about water level, affecting draining during programmes. This is a common enough cause, but it needs inspection inside the machine.

5. Wiring and connections Check the pump wiring plug and harness for loose or overheated connections.

If all of the above look fine, then yes, the pressure sensing system or control board become more likely, but I wouldn’t jump straight to the PCB. If you’re not confident with live electrical testing, it’s best left to an engineer. Any mains-related checks should be done by a qualified appliance engineer.

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