Works as a regular test light and when you push the button on the tool it applies an 800mA load at 12V DC to easily check for voltage drop on circuits. 
The display will indicate the voltage drop when the button is pushed.
Displays voltage under load to tell if circuit has problems like corrosion, resistance, or faulty connections. 48" cord with heavy-duty alligator clamp for secure connections. 
Not computer safe with load applied.
Not for use on airbags.