Circuit tester for cars 12/24V DC with 4M cable and overload protection1、This power probe can help you quickly identify the positive and negative polarity of cables and plugs. The red light indicates positive polarity, and the green light indicates negative polarity. 2、You can also test the continuity with the help of the auxiliary ground wire. Check the continuity of switches, relays, diodes, fuses, spark plugs, and circuits. 3、Fast track short circuit, when the fuse blows, it may be caused by a short circuit or a sudden increase in component load. The circuit tester can help you trace the problem cable and find the breakpoint. 4、For some components that require a large current to flow through the negative terminal, the short‑circuit protection circuit tester can immediately test the bad ground contact and start lead. 5、The test pen has an overload shutdown protection function. If the current or load is too large during power distribution, the test pen will automatically disconnect to protect the battery and issue a buzzer warning. 6、The insulating material used in the electrical tester has passed the CCC national safety compulsory certification, which is safe and reliable. It is widely applicable to all 6-24VDC vehicle electrical systems. 7、With a 4 meters long cable, you can easily test. This device is the best electrical tester to reduce the diagnostic time of automobile electrical systems.