Presently, no definitive technique has been reported that measures the onset-of-precipitation of asphaltenes from a hydrocracker product at process conditions. In the present paper, a detection technique utilizing heat transfer analysis is presented. The method is suitable for the high temperature and pressure conditions in upgrading and is based on a heat transfer analysis of the precipitated layer. The modeling of the technique is provided, as well as details of the heat transfer vessel. Results from glycerol and corn oil model fluid experiments and simulations demonstrate the validity of the method Preliminary experimental results for Cold Lake bitumen are presented along with recommendations on how the method will be further improved.