How To Test For a Bad Ground
A bad ground can be tough to track down. This video shows you how to run a separate ground cable to figure out where your ground issue might be.
Testing for a bad ground. Often a lamp looks like something’s wrong. We change the lamp, we make sure it’s getting full voltage, but it still looks like it’s not as bright or as strong as it should be. The problem is often a bad ground wire. The test is easy and only requires a jumper lead. Connect one end of the lead to a known good ground. Part of the body, the engine, or of course the battery, will be good. Connect the other end right where the existing ground meets the lamp socket. If that makes the light improve, you have a bad ground. This car has a bad ground.