An alternator is an important part of the vehicle’s electrical system. An alternator recharges the car’s battery while the car is running and provides power to key car parts (i.e. headlights, starter, dashboard lights). Your alternator is the reason your dashboard lights stay lit, your headlights are bright, heater running, radio cranking out the tunes, and all those million other electrical components keep working.
So how can you tell when your alternator has gone bad? What signs tell you it’s time to replace an alternator? Because the alternator provides power to the battery, it can be incredibly hard to tell if the source of your car problems is the battery or the alternator—and you don’t want to spend a lot of time trying to diagnose the exact source of the problem. Some people may try to tell you to run the engine while disconnecting the negative cable of a pair of jump start cables; this method can damage the electrical system of the car. Instead, schedule an appointment with a mechanic if you notice any signs of a bad alternator.
When alternator bearings are worn, the damaged bearings can let out a squeal that is noticeable when the hood is open and outside the vehicle. Contact a mechanic to find out the possible source of the squealing noise (other possible causes of a squealing car are listed here).
While a battery provides the initial power that starts your car, an alternator is what keeps the car going. If your car starts (or jump starts) but stalls after it starts up, a failing alternator could not be providing enough power to get you down the road.
If your car starts rough, doesn’t start at all, or makes a clicking sound, an alternator could be the cause. The clicking sound typically occurs after the key turns in the ignition.
The power supplied by the alternator keeps the headlights and dashboard lights running. When an alternator is failing, the headlights or dashboard lights may seem dim when driving. Similarly, other electrical components can start to slow down because of a weak power supply from the alternator (i.e. slow power windows or seats).
Dashboard warning light
Most vehicles, especially modern vehicles, have a dashboard warning light notifying the driver when there is a problem with the electrical system. The warning light may have the words ‘ALT’ or look like a battery; contact a mechanic as soon as the battery comes on to prevent being stranded.
Random dead battery
Modern batteries are manufactured with enough power to run a vehicle, but not for the long-term. A battery can only keep a car running for so long without an alternator before the battery dies. Don’t automatically buy a new battery; take the car to a mechanic to find out if the cause is a bad alternator.
An alternator has a lot of parts inside and around it; if any of these parts corrode or start to wear, you may start to smell an odd odor (i.e. electrical or burning smell). Schedule an appointment to find out the source of the smell and the problem.