Quooker Combi hot water is only lukewarm

The hot water function (i.e. not boiling) gives only lukewarm water. This is usually caused by calcification of the connection hose to the mixing valve. First check whether it is clogged.

If it is clogged, it is best to replace it with a new Quooker insert.

If this is OK, then the mixing valve may be defective/polluted and can be replaced.