Thermal contact conductance is very important in many heat transfer applications, such as electronic packaging, nuclear reactors, aerospace and biomedicine, among others. The determination of the thermal contact resistance/conductance is a very difficult task. The objective of this paper is to present a methodology to estimate the spatial variation of this parameter without intrusive measurements. The methodology presented is formulated in terms of a reciprocity functional approach together with the method of fundamental solutions. The solution is composed of two steps. In the first step, two auxiliary problems, which do not depend on the thermal conductance variation, are solved. With the results of this pre-processing, different thermal conductances can be recovered by simply performing an integral. Thus, the methodology is extremely fast and can be used to detect flaws in different materials in a short time. (C) 2013 Elsevier Ltd. All rights reserved.