Abstract: A circuit tester indicates the presence of power at an outlet and the continuity of a resistive load connected to the outlet. The tester is particularly useful as an automotive block heater circuit tester. The tester has a housing with a male end equipped with the prongs conventionally found on a male electrical plug and a female end with a socket of the same configuration as a conventional female electrical outlet. One of the sockets is divided into inner and outer terminals that are sequentially engaged by the mating prong of a male plug as it is inserted into the female end of the tester. A lamp and a resistive circuit are connected into this structure in such a way that when the tester is plugged into a live outlet, the lamp is illuminated brightly. When a male plug is inserted into the female end of the tester, the lamp initially dims to confirm continuity of the load and then brightens as the male plug is fully seated in the socket.