MDS Diesel Service Blog

Alternator Replacement

1/17/2014

This is the first in a series on routine maintenance. These posts will cover basic maintenance that applies to all trucks.

Trucks of all varieties need regular maintenance

The Ford Super Duty is no exception. Our customer with a 2003 6.0 super duty came in with the request to change his alternator. When we double-checked the volts on the alternator with our multimeter, the results were obvious, this truck was in need of an alternator.

The alternator should be putting out more volts than the battery has, in order to keep the battery charged. If the alternator is generating the same or less than the battery charge, then it is time to change the alternator. Other signs that it is time to change the alternator are:

A red warning light on dash
Intermittent red warning light on dash
Dim lights- most often you will notice the headlights are dim, sometimes the interior lights will also dim
Slow cranking
Dead batteries

Before replacing the alternator the battery charge must be 12.5 volts. The alternator acts as a voltage maintainer, it is not a battery charger. If your battery is dead to begin with you will over work the brand new alternator, or it may not work at all!

The voltage regulator (a component of the alternator) needs to be controlling the voltage output between 13.5 and 14.2 volts with the engine on and no load. This range will ensure your battery is charged correctly.

Another cause to replace your alternator would be if the voltage regulator is overcharging your batteries, causing them to spew acid. In this case the readings on the alternator would register over 14.5 volts.

Nearly all vehicles run on a 12 Volt system and the above standards apply, including all size trucks, semis, cars, motorcycles and boats.

Updated 2/21/14

5 Comments

Devon Horn link

3/14/2017 02:35:32 am

Alternator is used in a car in order to charge the battery and to power the electrical system when its engine is running. Alternators are also cheaper, lighter, reliable and more efficient which indicates that the conversion of AC to DC is now much easier and efficient. In some cases alternator may stop working if they are charging several electronics at one time. So, when we are going to replace an alternator in a car, we must be sure enough that the alternator is dead or in on the way to die. Your blogs gives a lot of idea about alternator and also delivers some warning signs by which one can easily identify that the alternator needs a replacement. Seriously I did not have much knowledge about alternator though I have been driving my AUDI for last 4 years. I found one point very unique that was checking the battery charge whether it is 12.5 volts or not before replacing an alternator. In one word your article is very informative and useful and everyone should keep all these in mind when they are going to change or replace their car alternator. Thank You for sharing this.

Harload Reed link

6/26/2017 02:36:51 am

The function of the car alternator is to provide electricity to power the accessories such as light, radio etc. It also helps to charge the car battery. It basically converts mechanical energy in the engine into electrical energy via induction. But one thing which is quite obvious that the performance of alternator gets deteriorated over the time. Well, in that case it must be replaced with a new one. Thus, I would like to tell that one should take the help of an expert while going to replace his car alternator.

Fred layman link

11/29/2017 01:52:10 am

The tips you have given here are very helpful in replacing an alternator. Vehicle alternator should be maintained at a regular interval, as damaged alternator could damage the battery and other electrical systems. If any clue that indicates, the alternator is not effectively working or it is totally damaged, then it should be replaced by a new one at the first place. The alternator replacement should be done near a trusted and certified repairing center and according to the manufacturer's recommendation which is best for your vehicle. Thank you.

Ryaln jones link

1/22/2018 03:54:37 am

Thank you for sharing such in-depth article about alternator replacement. Alternator plays a key role by maintaining the voltage of the battery and any types of damage to the alternator could affects the performance of the vehicle. I didn't knew that the voltage of the battery should be 12.5 volt before the replacement of the alternator. My battery showing poor performance in recent times. I thinks it may be the damaged alternator, which is affecting the performance of the vehicle.

Chelsey Bobby link

4/16/2018 05:00:45 am

Alternator is used in a car to charge the battery & to keep the electrical system running. The main function of alternator is to change AC to DC. It basically converts mechanical energy in the engine to electrical energy via induction. When the alternator generates the same or less than the battery charge, then it is time to change the alternator. When we notice that the headlights are dim,a red or intermittent red warning light appears on dash or batteries become dead it indicates that it is the time for alternator replacement.

Alternator Replacement

Trucks of all varieties need regular maintenance

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