Introduction
Have you ever had problems with your car not starting? It could be a problem with your alternator! The alternator is a crucial component of your car’s electrical system. It’s responsible for powering the battery and all your car’s electrical accessories while the engine is running. A bad alternator can lead to a dead battery and stranded you in the middle of nowhere.
If you suspect that your alternator is bad, it is important to diagnose and fix the problem as soon as possible. In this article, we will go through the common signs of a failing alternator and provide you with a step-by-step guide on how to check if alternator is bad.
Signs & Symptoms of a Bad Alternator
The following are some of the common signs that indicate a bad alternator:
Dimming headlights or interior lights
One of the most common signs of a bad alternator is dimming of headlights or interior lights. This occurs when the alternator fails to supply sufficient power to the car’s electrical system, and the battery tries to compensate for the lost power by draining itself.
Burning smell or smoke
If you smell a burning smell or see smoke coming from the alternator, then it’s an indication that the alternator is overheating. Overheating results from a faulty alternator voltage regulator or problems with the wiring.
Strange noises (e.g. clicking, grinding)
Noises coming from the alternator, such as clicking or grinding, may indicate a bad bearing caused by a worn-out belt, an over-tightened belt, or inadequate lubrication.
Warning lights on dashboard
If you see warning lights like the battery warning light, check engine light, or the oil pressure light, it could be a sign of a damaged alternator or a weak battery.
Issues with electrical accessories (e.g. radio, power windows)
If your car’s electrical accessories, such as the radio, power windows, and air conditioning, are struggling or not functioning properly, then it’s a sign that they are not receiving enough power from the battery
Step-by-Step Guide to Checking Alternator Efficiency
Below we will walk you through a simple process to check the efficiency of your alternator.
Step 1: Prepare your tools and safety equipment
To check if your alternator is bad, you will need a few essential tools like a voltmeter or an ammeter and a pair of gloves to ensure your safety. Make sure to protect yourself by wearing safety glasses, gloves, and other protective gear before you start.
Step 2: Check battery voltage
Start by checking your battery’s voltage with a voltmeter before starting the vehicle to measure its cold cranking amps. Then, check it again when the engine is running to see if it has charged. The voltage reading should resemble the following:
- 12.5 Volts or more – Fully charged
- 12.3 Volts – 75% charged
- 12.0 Volts – 50% charged
- 11.8 Volts – 25% charged
- 11.5 Volts or less – discharged
Step 3: Check alternator output voltage
Next, start your car and let it run for a few minutes to measure the alternator’s output voltage using a voltmeter. You can connect the voltmeter to the battery’s negative and positive terminals to take the reading while the engine is running. The voltage reading should be between 13.7 and 14.7 volts. Anything above or below this range is a clue that the alternator may be failing.
Step 4: Check alternator output amperage
To check the alternator’s output amperage, you will need to make use of an ammeter. To measure the amperage output, place the ammeter in between the positive terminal and the positive battery cable. As the engine runs, it should show around 30 amps of reading when in good condition.
Step 5: Interpret the test results
By interpreting the results obtained after the necessary checks, you can decipher if the alternator is bad. A malfunctioning alternator will show readings outside the standard range and may need to be replaced.
Testing Procedures for Confirming a Bad Alternator
If you’ve performed the above tests and still suspect that your alternator is faulty, there are specific testing procedures to confirm its state.
Alternator output test
The alternator output test examines the armature windings and all connections in the circuit. Technicians use this test to determine excessive amperage output, voltage output, or open circuits in the stator, rotor, wiring, and diodes.
Battery load test
A battery load test checks the battery’s cold-cranking amps and capacity to hold a charge or discharge under different loads. Technicians often use this test to uncover issues with the battery and alternator working together..
Alternator diode test
In the alternator diode test, a technician measures the electrical continuity between each of the three AC stator output wires and the battery ground. This test shows whether any of the six diodes are faulty and, in turn, can cause the battery to discharge.
Alternator ground test
The alternator ground test checks if the alternator is well grounded. It involves taking a voltage drop test between the alternator case and its negative terminal to check for ground losses.
Video Tutorial on Checking Alternator Efficiency
Visual content can help you understand better on how to undertake tasks. Below is a link to the video tutorial that demonstrates the process of how to check if your alternator is bad.
Here is the link to the video https://youtu.be/wZmptJwfHcI.
Simple DIY Tips for Testing Your Alternator
Here are some simple DIY tips to help you check your alternator’s efficiency and prolong its life:
Check battery terminals for corrosion
Corrosion is a leading cause of battery and electrical connectivity problems. Ensure that your battery terminals are clean and free from corrosion as this can affect the alternator’s functionality.
Inspect the alternator belt for cracks and fraying
Belts are prone to wear and tear with time. Ensure your alternator belt has no signs of cracks or fraying since it’s the belt that transmits power from the engine to the alternator and can lead to alternator failure.
Ensure proper grounding between the alternator and the engine
The engine serves as a ground for the entire electrical system. Any damaged or loose grounding cable, strap, or wire can hamper proper grounding between the engine and the alternator. Replacing or repairing damaged grounding straps and cables will help improve your alternator’s efficiency.
Q&A/FAQ
Why can a failing alternator cause my car not to start?
The alternator is responsible for producing and supplying power to the battery, which, in turn, starts your vehicle’s engine. If your alternator fails, it won’t supply enough power to the car’s electrical system, resulting in a dead battery and unable to start.
Can a bad alternator drain the battery quickly?
Yes, a malfunctioning alternator can cause a quick battery drain. The battery will have to compensate for the lost power from the alternator, and this will lead to rapid battery discharge.
How long should a car alternator last?
On average, an alternator can last up to seven years or 100,000 miles before failing and needing a replacement.
Conclusion
It’s essential to diagnose a faulty alternator early on to prevent further damage to your vehicle. We hope that this guide will help you identify the signs and symptoms of a bad alternator, understand the testing procedures to check for a failing alternator, and offer you some simple DIY tips to test your alternator efficiency at home. Remember that a correctly functioning alternator is crucial for your vehicle’s longevity, so take action immediately if you have a hunch that it’s not working correctly. For repair or replacement needs, contact a reliable mechanic for assistance.
