There were plenty of car stores that used test lamps, not so many people using a digital multimeter. Are you really "better" than the other than searching for energy?
Completely! The test lamp looks like a sharp-pointed screwdriver and has a small bulb and an earth wire or cable. It works with the bulb's ground, and after it comes into contact with a power source, terminates the circuit and lights the bulb. This is the simplest way to test the power supply because the bulb or power is on, or if it is not, there is no current.
The problem of testing this type of vehicle today is the complexity of each circuit within the fastener. When you set the test lamp to a "hot" wire, it generates a small "arcuate" current that can shorten the more sensitive devices, such as the airbag sensor or relay. Actually, I saw a mechanic blow airbags out of a new BMW M3 during the test. In most cases, this does not hurt, but if so, the cost can be very high.
I recommend using a digital multimeter to test the circuits. These are very accurate and they can tell a lot of useful information, such as voltage, amplifier and ohms, all of which are essential to know when building a good sound system.
These multimeters work a bit differently than a standard test lamp. Generally, there is an element on the board that supplies power to the power supply, so it does not pull the power of the power source, reducing the tendency to "arc" the power source. They are usually safer for sensitive systems than their test lamps.
Digital multimeters are a great tool for car audio installers, as they can help you find the system's problems. They are also needed if other 12-volt car accessories are installed. A test lamp will flash, but it will not tell you whether you get the right voltage and amplifier. With a multimeter, you can start reading the components and work until you find the wrong operation.
Multimeters range from about $ 10.00 to $ 100.00 and depending on the level of work and how accurate it is which will work for you. It's a great investment and saves a lot of headaches if you find a problem with a system.