Detecting An Alternator Failure

Jim Luff
Posted on September 14, 2016

(Creative Commons image by Dave_7)
(Creative Commons image by Dave_7)
Without a doubt, alternators are one of the most common mechanical failures a chauffeured vehicle will experience.

The constant drain on the electrical system from high powered stereo systems to the dazzling array of lights in a party vehicle and constant A/C usage can kill an alternator on a hot day.

What Does Your Alternator Do?
The alternator recycles the power your battery uses while driving down the road. It restores the power the battery loses while supplying the engine, climate system, entertainment and host of other systems with the energy needed to run properly.

The battery is used to start your vehicle and keep it running. The alternator converts engine power back into the battery. The vehicle’s electrical system depends on an optimally running alternator. When the alternator fails, you will soon be left on the side of the road with an overheated engine and the inability to restart the vehicle as the battery will be depleted.

Warning Signs:

Dim Lights
If the alternator starts to die, you might notice your headlights and/or dash lights begin to dim. A waning alternator may cause other electronic accessories such as power windows and/or power seats to operate more slowly than usual.

Warning Light
Most vehicles have a dashboard warning light that alerts you when the alternator is on the fritz. Usually, the light will be shaped like a battery or say ALT. This light may only trigger if you are using multiple electrical components.

Weak or Dead Battery
A car battery will only last for a few years. As much as the alternator replenishes your battery, it can only recharge it to the point where it accepts a charge. If the battery is really weak or dead, the alternator cannot bring it back to life. To troubleshoot whether the issue is the alternator or the battery, just charge the battery and restart the vehicle. If the battery is weak or dead, the car will run, but the lights will again become dim after a short time, indicating a problem with the charging system. If the vehicle has difficulty starting after the battery is fully charged, there is likely a problem with the alternator.

Weird Smells
An alternator works with a system of belts. If a belt is not turning freely, the excess friction will cause the belt to heat up, which produces a burning rubber smell. If you catch a whiff of a smell similar to that of an electrical fire, this could indicate the belt is slipping on the alternator pulley, causing poor alternator output. Tightening the belt often does the trick. If the situation arises where tightening your belt does not fix the strange smell and alternator output, we recommend having your alternator tested at a battery shop or auto-electric shop.

Odd Sounds
Many different parts spin inside your vehicle’s alternator to produce electrical current. If one of these parts wears or breaks, it could grind or whine. Specifically, worn out bearings inside the alternator have been known to cause such noises. If the bushings the alternator is mounted on have gone bad, you will hear it.

Visual Inspection
If you are experiencing problems with the electrical system, the alternator might be fine because the problem could be with one of the belts connected to the alternator. By doing a visual inspection of the engine compartment, you can determine if a belt is too loose or too tight. If a belt is cracked or worn, you should be able to spot that as well.

Related Topics: Jim Luff, maintenance, maintenance tips, Shop Talk blog, vehicle maintenance

Jim Luff Contributing Editor
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