1. Connect one of the test light probes to the negative battery terminal or vehicle ground.
2. Connect the second probe to a connection on the circuit under test, preferably as close as possible to the battery or fuse.
3. If the control lamp lights up, voltage is present: this means that the part of the circuit between the connection and the battery is good.
4. Continue checking the rest of the circuit in the same way.
5. When you find the point where there is no voltage, it means that the source of the fault lies between this point and the last point where the voltage was present.
6. Most of the problems are caused by a bad connection.
Attention! Do not forget that in some circuits there is voltage only if you turn the key in the ignition switch to a certain position.