Alternator Problems? Wheelco Has Answers!

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Do you have questions about how alternators work? How about common problems and symptoms? Know the basics but do you need help with testing or installation? Wheelco has the answers you need.
Open Front Semi Truck

Do you have questions about heavy duty alternators? Wheelco has the answers you need from install to troubleshooting!

How does an Alternator work?

An alternator is an electrical generator that converts mechanical energy of the engine’s rotating crankshaft to alternating electrical energy. This electrical energy, or current, is called induction. This current charges everything from headlights to hydraulic lifts, making it a vital part under your hood. 

Parts of an Alternator

An alternator can consist of several parts: diode rectifier, bearing, rotor assembly, voltage regulator, DC generator, pole core, stator, outer cover, pulley, etc.  Before installation, or if your alternator is not working properly, you can visually inspect some of the components without taking it apart. 

Parts of an Alternator

External Fan

1 of 4

Shaft

2 of 4

No Pully

3 of 4

Pad Mount Style

4 of 4
Parts of an Alternator

Voltage Regulator

1 of 3

Hinge Mount Style

2 of 3

Rectifier

3 of 3

How does an Alternator Create Electricity?

A belt, driven by the engine, spins the rotating armatures inside a rotor. As the armatures rotates, it brushes against copper-carbon slip rings on its shaft causing an electromagnetic field. Inside the rotor is the stator, which is essentially a set of wire coil windings. These wires inside the alternator generates electricity and cut through a magnetic field that is created by a revolving rotor. This, in turn, induces an electrical current. This electric current, induction, is an alternating current, which means that the direction of flow goes back and forth every time the rotor turns. In order to harness the electricity, it must be rectified. To rectify a current simply means to turn it into a one-way flow, or direct current. The alternator’s set of diodes do this. Then the current can properly charge the battery.

Correct Alternator Voltage

Most alternators have an output between 13 and 14.5 volts to maintain at a constant level of electricity. When your voltage output goes above or below a pre-set limit, you will start to notice that your heavy-duty truck isn’t working properly. We’ll cover signs and symptoms next, so you know what to look for.  

Top 10 Signs of Alternator Problems

If your voltage is outside this pre-set range, the light on your dashboard is likely to turn on. This is usually an “ALT” or “GEN” or looks like the shape of a battery—but that doesn’t mean your battery is to blame. It might very well be your alternator so here are the top signs/symptoms that it’s time to replace your alternator.

  1. Dashboard warning light comes on
  2. Dimmed or flickering headlights
  3. Odd smells like burnt rubber or rotten eggs
  4. Growling or squealing sounds from under the hood
  5. Slow cranking or difficulty starting
  6. Dashboard flickers
  7. Dead battery
  8. Broken or loose connections
  9. Bad belts (loose or hanging off the engine block)
  10. Slow accessories (example: windows get stuck open)

Starter and Alternator Diagnostic Worksheet

Download our diagnostic starter and alternator worksheet for your convenience. That way you have step by step instructions to test your parts before bringing it in to see one of our service technicians.

Confident enough to install the alternator yourself? Great, but if you’d like to have a guide on the ready in case you run into unforeseen problems, download our installation guide

Videos & Alternator Installation Guides!

Video! We have videos specific for installing heavy duty starters and here is an installation video specific for heavy duty alternators.

You Deserve the Best in Alternators and Starters

Wheelco stocks premium brands like MitsubishiDelco Remy, and Meritor. Our mechanics and experts trust these brands in their own vehicles.

If you do need to bring in your rig, Wheelco Truck & Trailer offers full-service repair and complete electrical system services. Whether it’s your alternator or even your battery or starter, Wheelco is your service center. Our professional, industry-trained mechanics use the latest technology and tools for diagnosis.  

Wheelco Services offered in Sioux Falls, SD, Mitchell, SD, and St. Paul, MN.

  • Diagnostic Troubleshooting
  • Component Benchwork
  • Starter Diagnostics and Replacement
  • Alternator Diagnostics and Replacement
  • Battery Diagnostics and Replacement
  • Cable & Wire Replacement
  • Lighting Installation & Repair
  • Computer Controls / Multiplex Wiring
  • Preventative Maintenance & Inspection

About Wheelco Truck & Trailer

At Wheelcobeing customer driven is more than just a motto we live by. It means that our employees will do everything we can to best serve you, our valued customer.

Customer driven is more than just offering you advice, giving time-honored service or contributing the latest tech-support. It’s about being there—whenever and wherever you need us—in-person, over the phone or online.

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