Car Not Starting? Find Your Culprit
By: Eric Wasson
Testing your battery is very important- it can help ensure that your battery will function when you need it most. Battery care and maintenance is key to making sure that you catch your battery before it fails you. And while we all recognize the importance of battery maintenance throughout the battery’s lifetime, we also know that sometimes your car may not start, and you may be unsure whether the problem lies in your alternator or your battery. Before you go ahead and buy a battery without running tests, check your battery to see if it really is the culprit. If not, you could end up wasting money on a new battery that will not actually solve your real issue.
Important Safety Note: Before you do anything with a battery, you should wear eye protection and keep any open flames away from the battery. This includes cigarettes and other smoking products. Batteries produce hydrogen gas that is extremely flammable. Batteries contain sulfuric acid, so you should also wear latex gloves to keep battery acid from burning your hands, specifically if you are dealing with a non-sealed battery.
Testing your battery is the first step – batteries typically have a shorter life than alternators, whose lives usually extend about 2 years longer.
Step 1: Inspect The Battery Terminals
When inspecting the battery terminals you want to look to see that your terminals do not have any sign of corrosion. If you do see corrosion on the terminals, you want to remove the clamp from the black negative terminal, and then the red positive clamp. Using a wire brush and a battery cleaner can make the task much easier.
Step 2: Inspect The Wiring
Check the wire going into the terminal clamps to ensure they are fitting snugly, and are free of damage or corrosion. If the terminal caps are heavily corroded, we recommend replacing them, either with a basic replacement, or a zinc replacement for a better electrical connection.
Step 3: Check Your Voltage
First, make sure your battery has a full charge (roughly 12.6 volts). If it hasn’t been charged, charge it first. Once you’ve fully charged your battery, attach one of your multimeter’s test leads to the negative terminal and the other to the positive terminal. Check the voltage readout. Any number lower than 12.6 volts means that your battery is weak and needs replacement.
Step 4: Start Your Engine
Lastly, you’ll want to test your battery by starting your car. Attach one of the multimeter’s test leads to the positive terminal, and the other to the negative. Have a friend start your vehicle while you watch your multimeter. If your voltage goes below 12v while your vehicle is being started, it could be that you have a defective starter that is pulling excessively on your battery, or your battery is weak and needs replacement.
After testing your battery, you may see no issues. That means it is time to move on and test your alternator. The alternator is important- it is used to charge your battery while the engine is running. An alternator that is overcharging or undercharging could all cause serious problems with your battery. Before you run any test on your alternator check to see if the power belt around your alternator is tight and that it is spinning while the engine is running. Furthermore, check your wiring from the alternator to the battery for bad signs. Look for damage, loose wires, or misconnections between the two. Then you can test your alternator.
The Load Test
Step 1: Start Your Engine
Turn your key and start your vehicle.
Step 2: Turn On Accessories
Power up every electronic device you have available in your vehicle, such as your radio, air conditioning, windshield wipers, heated seats, or GPS. Newer cars have more devices, so try to add as many as possible to ensure your test is most effective.
Step 3: Check Your Voltage
Attach one multimeter lead to the positive terminal on your alternator, and the other to the negative. Your voltage should be between 13 and 15 volts. If your voltage is outside of this range, your alternator is likely bad.
Step 4: Check The Surface Charge
When you power down your vehicle the voltage should read around 12.9 volts and it ought to slowly decrease to about 12.7 volts. This is your surface charge, and is a sign your alternator is working fine. However, if it does not decrease slowly to 12.7 volts, you may have a faulty alternator.
Disclaimer: This article was written with help from these articles. We recommend looking through them if you have more questions. If you are still experiencing issues starting your vehicle, we recommend taking your car into a repair shop you know and trust.