6 Signs Your Alternator Is Bad Even Though Your Diesel Car Is Still Running

You’ve heard the story: People can still drive their diesel-powered vehicles with a bad alternator and this is true. Diesel engines are amazing feats of mechanical engineering, and they can keep running even when they shouldn’t be. A bad alternator does not always kill your diesel engine, but you will notice other issues while you drive. United Diesel lists what they are below.

Light Trouble

Even though your diesel engine is still running, a bad alternator does not have enough power to manage electrical components. One component that will reflect the loss of power is your vehicle’s lighting system. Your headlights and taillights will lose their brightness as will your interior lights.

One Light Will Work, Though

In newer vehicles, your battery dashboard light will turn on to tell you something is wrong with the electrical system. You might also have an ALT or GEN light on your dashboard and this will shine. ALT stands for alternator, so if this light turns on, you know you have alternator problems.

Battery Trouble

Since the alternator charges the battery and keeps it charged in both diesel and gasoline engines, you will also have battery trouble if the alternator is failing. This includes difficulty starting your vehicle or, in severe cases, the inability to start your vehicle if the battery is completely dead.

Burning Belt Smells

A diesel engine’s alternator uses a system of belts to generate the friction required to produce voltage. As with any belt in your diesel engine, if there is something wrong, you might smell burning rubber. Usually, this odor is caused by a belt that is unable to turn freely or is slipping.


Grinding or whining noises coming from your diesel engine could be coming from the alternator. If the moving parts of the alternator are broken or worn, they will make noise. Usually, bearings inside the alternator wear down over time and this causes the grinding or whining sounds.

Connecting Belts

The belts that connect your alternator to other engine parts could also be the problem. If you can locate your alternator in your diesel engine, you can visually inspect these belts for wear and tear. Check them first with your engine turned off. Then, turn the engine on and watch them for problems.

United Diesel in Flowery Branch, GA, can replace your diesel vehicle’s alternator when it has died. Call us today for an appointment at 770-967-8333.

Photo by loraks from Getty Images via Canva Pro