Originally Posted by Danthurs
You can pick up a multimeter, (DVOM) for under $20.
A test light is far more helpful and easier to use than a meter. You can even make one easily by obtaining a small car light bulb in a socket and fix 2-3 foot wires to the socket. To use, clip one wire to a car ground and put the other wire on the suspected electrical contact. Light either lights or doesn't indicating +12v or zero volts. Simple presence of voltage is all that'* needed to trace or chase electrical faults. Best purchased ones are the cheapest ones. Worst are those with added features like +6v or continuity or with probes for ground instead of a bare wire or clip as probes don't stay put.
GL One does occasionally need a meter, analog or digital, to determine alternator condition. But test light is easiest to use because you don't need to take your eye off the contact being tested to read it, the presence of light is obvious without having to reorient the meter.