Here is a compact wireless tester from Performance Tool for quick diagnosis of 12 volt automotive relays. It allows you to check the condition of the relay winding and its contacts. The result of the test is indicated by LEDs - green light is on when the relay is good and red light is on when it is bad. The tester is quite compact, it is no bigger than Tetris, and runs on only 4 batteries. Effortless to use, does not need to be connected to the on-board network of the car. It is a convenient device for express diagnostics, which every car enthusiast should have in his garage.