Abstract: A cartridge style, pop up, differential pressure indicator includes a threaded body member, a cover structure and a cylindrical indicator button, which carries a magnet at its lower end, and is slidably supported in the cover for movement between a depressed, hidden position and an extended indicating position. The button is engaged at one side by a leaf spring which in the depressed position urges a lip on the button under a ledge in the cover to serve as a detent. A piston slidably supported in the body is subject to differential fluid pressures and carries a magnet at its upper end, poled in a manner to repel the magnet in the indicator button to urge the latter against the bias of the detent spring and upwardly to the extended, indicating position. A semicircular bimetal strip supported in the cover engages the detent spring at lower temperatures to prevent false release of the indicator button due to cold weather, high fluid viscosity situations.