Qualitative reasoning about electrical systems has reached a level of achievement which allows it to be used for applications on realistic automotive circuits. The type of circuits for which it is most effective can be characterised as circuits with a single steady state for each combination of inputs. Many automotive circuits with more complex overall behaviour can be approximated using this type of modelling by representing the behaviour of more complex components only at a functional level, or by judicious use of simplifying assumptions. This paper will consider examples of circuitry in modern cars where such approximations of behaviour are unsatisfactory, and will examine the modelling issues that are thrown up by these cases, in order to identify challenges for qualitative electrical reasoning against which future advances in the field can be assessed
