Why has my vacuum cleaner lost suction?

Start with the checks your vacuum’s own manual allows, rather than taking the machine apart. First identify the make and model, then look up its instructions for checking the bin or bag, filter, selected mode, and accessible tools or passages. Dyson’s support guidance for the V12 Detect Slim lists a filter needing washing, an unsuitable power mode, dirty or blocked tools, and a cyclone needing cleaning as possible causes of poor performance or lost suction. Those are model-specific possibilities, not instructions for every vacuum. [S1]

Before inspecting anything, turn the vacuum off and follow the manual’s directions. Don’t run it with a bin, filter, cover, or other protective part removed.

Check the bin or bag first only if your manual identifies it as user-checkable, and follow its instructions for emptying or replacing it. If it looks empty, move on to the next approved check rather than forcing open a panel or probing inside the machine.

For the filter, don’t assume that it can be washed. Only clean it if the instructions for your exact model say it is washable and explain how to handle it. Dyson mentions washing the filter as a possible check for the V12 Detect Slim, but its page does not establish that every vacuum has a washable filter or provide a general procedure for other models. [S1] Don’t rinse a filter, reinstall it, or use the vacuum with a part missing unless the model’s instructions permit that specific step.

Use only the manual’s directions for clearing an obstruction in an accessible tool or passage. Dyson’s V12 Detect Slim guidance includes checking for blockages and mentions dirty or blocked tools, but that does not establish where every model may be safely inspected or how to clear it. [S1] Don’t push an object into a passage or dismantle a section unless the instructions specifically describe that check.

A useful worked note is: “Tool opening: [visible debris / no visible debris]; checked only the accessible area described in [manual section]. Suction still seems reduced: [yes/no]. Bin or bag: [observation]. Filter: [checked according to instructions / not checked].” This keeps observations separate from parts you have not checked.

Use this as a tracking order, but let the manual decide which checks apply and how to do them: identify the model; check the bin or bag; check the filter instructions; confirm the selected mode; inspect only accessible tools or passages. Dyson lists mode, filter, tools, and cyclone among possible causes for the V12 Detect Slim, but that does not mean every vacuum has those parts or supports the same checks. [S1]

Stop if a step would require opening a sealed area, removing a protective part for operation, or guessing how to clean a component. Refit all protective parts before using the vacuum. If the approved checks don’t explain the change, note the model number and what you checked, then ask the manufacturer or a qualified service provider for model-specific guidance.