In this study, the correlation of morphology, temperature dependent electrical conductivity and solid-state relaxation dynamics of melt-mixed polyamide 12 (PA-12)/polypropylene-multi walled carbon nanotube (PP-MWCNT) based ternary nanocomposites has been systematically investigated. Selectively confined functionally conductive masterbatch dispersed in nylon matrix with structurally ordered co-continuous morphology enhanced the electrical conductivity due to double percolation phenomenon by virtue of their differences in melt viscosity, polarity, surface energy and similar processing window of PA-12 and PP-MWCNT. The stability of the conducting polymer nanocomposites and the correlation of temperature sensitive electrical behaviour with the endothermic transitions and dynamic-mechanical relaxation transitions in the temperature range of −20 °C–200 °C is also explored. Polymer nanocomposite based thermo-sensitive materials substantiated four distinct regimes highlighting the network build-up or restoration assisted conductivity. Our study demonstrates the tunability of temperature dependence of electrical conductivity by controlling conducting channels via manipulating the ratio of PA-12 to PP-MWCNT composite filler for temperature dependent current terminating electrical devices. The reproducibility of such temperature sensitivity has also been explored.