Usually when there are electrical problems in an automobile, the battery is the first suspect as forthe electrical breakdown. But sometimes, it is the car’s alternator system that may be failing. Dimming headlights or a slow cranking engine indicate the starting signs of alternator trouble. This is actually a potential problem with possible detrimental effects to the entire circuitry of the automobile. Alternator testing will show whether the problem is actually the alternator system; and if not, to rule out other possible causes such as faulty wiring, possibly dysfunctional voltage regulators or a depleted battery.
It is important to bear in mind that you should not do this as an alternative to alternator testing: a battery cable should never be disconnected while the engine runs to see how the alternator functions. Doing so could damage further other electrical circuitry of the automobile.
To perform alternator testing, you should have a multi-meter at hand. Open the hood to see the car battery clearly. Locate the alternator.Inspect the belt for looseness (it shouldn’t be loose). Adjust the multi-meter to 20 volts and then start the engine – now, check if the alternator belt is spinning properly without slips.
Place the positive probe to the red terminal of the alternator, and then place the negative probe to the metal car frame (not to the alternator itself – grounding it could damage it further). A functional or positive alternator testing result is around 13 to 14 volts.