Abstract: A device for detecting both low level and excessively high temperature of oil in an internal combustion engine or other oil container. The device consists of a semiconductive material which exhibits a peak electrical resistivity at a predetermined temperature. The semiconductive material is mounted on the interior bottom surface at the closed end of a metal cup which is suitably mounted and immersed in the fluid whose level and temperature are to be monitored. The semiconductive material is connected in series with a power supply and indicator light. If, at any point over a broad range of temperatures, such as -50.degree. F to +300.degree. F, the level of the liquid drops such that it does not contact the cup sufficiently the normal current flowing in the circuit will heat the semiconductive material past its peak resistivity thereby driving the current in the circuit past the level required to light the bulb and indicate a problem (herein a problem of low level).