Last week, we looked at what the alternator does and how it works. Identifying a faulty alternator is not always straightforward as usually something else gets the blame first, such as failing bulbs or an old battery.
Aside from a repeatedly flat battery, there are a few signs that might tell you that you have a problem with your alternator:
Vehicle owners tend to love and hate warning lights. We love them because they tell us that we may have a problem, but we hate them because they tend to be a sign that we are about to spend money. The battery warning light doesn’t just tell us that we may have a battery problem; it tells us that there may be a problem with the alternator, which supplies the battery with power. The light can come on sporadically depending on what you are using. For example, if you have your power-greedy air conditioning on and switch on your windscreen wipers, the light may come on. Switch off the wipers or the air con and the warning light will probably go off again. This sporadic warning is a sure sign that you have a power supply problem.
Dimming or flickering lights
As your alternator takes on electrical needs when your engine is running, an interruption to your lights means that there is not quite enough power to do what you want to do. As with the warning lights above, your lights may dim when you have your lights on then you put the radio on, or the windscreen wipers, for example. If you notice that the lights dim or flicker when there is additional power requirement, then it is very likely that your alternator is not functioning as well as it should.
A drained battery can be a sign that your battery is old and unable to hold charge completely, so the temptation is to replace the battery and assume the problem will go away. However, a dead battery can also be a sign that your power source (the alternator) is faulty. Before paying hundreds of pounds on a new battery, ask your garage or roadside repair service to run a diagnostic test on your battery to see what its capacity is. If your battery is in good condition, the alternator may be the problem.
If your alternator is not powering your battery properly, it could be a problem with the battery, the alternator, or the wires that connect the two. Failure to start your vehicle could be as simple as a loose connection which means that the alternator is not able to feed power direct to the battery.
Other signs that you may have a faulty alternator include sluggish starts or regular stalling, an electrical burning smell, or slow accessories. If you notice any of the above, make sure that you mention it to your garage mechanic or consult an alternator specialist so that they can check it over.