Abstract: Maintenance aid device (1) for a plasma torch (2) affected by a breakdown, comprising an expert system (3) successively determining subassemblies (4) of said torch (2), of decreasing size, likely to contain the brokendown element, by means of questions (QU) relating to the state of certain subassemblies (4), the response to these questions (QU) by an operator (14) being facilitated by the fact that said maintenance aid device (1) includes addressing means (10) able to read from a documentary base (8), and to display, information relating to a determined subassembly (4).Maintenance of complex plasma torches and use of a unique knowledge structure of the latter for other expertise besides breakdown repair.