Purpose - The purpose of this paper is to report a research in which fuzzy assessment of failure mode and effect analysis (FMEA) was examined on the design of rotary switches. Design/methodology/approach - In the case study reported in this paper, fuzzy FMEA of a rotary switch was analysed, starting from its individual components to subsystems. Failure modes were identified and the effect of these modes was studied, then the results before and after taking actions were compared. Findings - The usage of fuzzy FMEA enabled the reflection of real situation for determining the interdependencies among failure modes and effects of rotary switches with the incorporation of knowledge and expertise of experts. Research limitations/implications - The assessment has been attempted on a single rotary switch assembly. In future, this method can be applied in complex systems. Practical implications - The paper shows that the method enabled the decision makers to share information from various working groups. Originality/value - The case study has been conducted in a rotary switches manufacturing organisation and the results before and after improvement have been compared. © Emerald Group Publishing Limited.