Method and elevator controller for detecting a malfunction in an elevator

A method and an elevator controller (31) for detecting a malfunction such as elevator blockage in an observed elevator (3) is proposed. The method comprises: acquiring first data during an application phase, the first data correlating with at least one condition in the observed elevator (3); acquiring further data during the application phase, the further data correlating with the at least one condition in other elevators (5); determining a current relative behaviour of the observed elevator during the application phase based on a comparison of the first data with the further data; and detecting the malfunction in the observed elevator (3) based on an analysis of the current relative behaviour. Preferably, an information about a normal relative behaviour of the observed elevator (3) as learned in a machine learning procedure during a preceding learning phase may be taken into account upon analysing the current relative behaviour of the observed elevator (3). The proposed method may enable automatically detecting malfunctions in an elevator while reducing a probability of false alarms.