Now if you really want to be the "guy" on dc troubleshooting, get a power probe.
Makes you into a Merlin kind of guy for troubleshooting.
I have the III, you could buy a IV, but a II is all you need.
Call it a test light on steroids.
Features & Benefits for a II from Matco Tools (but you can get off Amazon)
Bad ground indicator
Short circuit detector
Kit includes: Power Probe II circuit tester, a 20' extension cable, battery hook up clips,a cigarette lighter adapter and a 9" extended tip. The kit also includes a blow molded case
Off the internet - "It was a few years ago, but I distinctly remember the day I first learned about Power Probe.
One of our technicians bought a Power Probe from the tool truck and used it to quickly diagnose an unusual lighting problem.
Power Probe 3He was so excited about how well it worked; he called a few of us over to check it out. We all played around with the Power Probe for a couple of minutes, turning on fans, lights, the fuel pump and even starting the car by activating the starter relay.
The tool’s unique troubleshooting capabilities were obvious to everyone and within a month almost every technicians in the shop owned a Power Probe and the guys who didn’t were asking to borrow mine.
The Power Probe was always a valuable tool, but there were still plenty of tests where I had to go back to the toolbox to get out my multimeter.
Power Probe has just released their most powerful version yet, the Power Probe IV, and let me tell you, my meter may never come out of the toolbox again!"