Automotive circuit tester with LED light for boats and trailers1、Easy to Diagnose: This circuit probe is an electrical tester designed to reduce diagnostic time for automotive electrical systems. Comes with a 4m cable for easy testing. 2、Multi Uses: Circuit detector can test for continuity, test for polarity, test for bad ground contacts, check switches, relays and the on off of diodes, fuses and circuits, track and locate short circuits. 3、Safety Tools: Automotive test probe is the useful tool to determine if power is present and also as a means of safely powering up fans, motors and electrical circuits. 4、Quick Identification: Help you quickly identify the positive and negative polarity, when the probe touches the positive +, the red light is on, and when the probe touches the negative ‑, the green light is on. 5、Wide Application: Quickly and efficiently perform testing of electrical systems, suitable for all 6‑24V systems, including cars, boats, trailers, relays and more.