Why your car isn’t starting.

  1. If the motor is cranking but not starting.

    1. This is probably not related to the battery, connections, or your charging system. You will have to look elsewhere for what other things to look at like fuel, ignition, etc.
  2. If the motor does not crank (and is not SEIZED UP):

    1. Battery not holding a charge. It worked when you drove it home but wouldn’t start in the morning.
      1. Bad cables or connections. Often corrosion and loose connectors are the cause of intermittent failure. But if the cycle is consistent, like it happens every morning after being fine at night or sooner, then check the other points below.
        1. Wiggle the terminals, make sure your connections are tight. You should not be able to rotate the connector or lift it off.
        2. Make sure the connections are clean – use 1/4 cup baking soda mixed with 2 cups of warm water and a brush to clean corrosion off of the battery terminals. Repeat until they are shiny clean. Or use a wire brush. Both the battery terminals, and the terminal connectors themselves should be clean.
        3. Make sure the wires are in good shape and not “hanging on by a thread” so to speak. If after market terminal connectors have been added, make sure that the wire attached to the connector has not corroded out.
    2. Something being left on in your vehicle is discharging the battery faster than normal. Often this is from a bad sensor (like trunk open, doom lights, etc.) or from something keeping the computer awake or a problem with the computer, or after-market electronics (stereo, etc.).
      1. The test for this is dependent on the average amount of time you’re experiencing between the battery being charged (like right after your vehicle has run for 10 minutes or more) and the time it takes to no longer have the power to start the car (like overnight). For example, if you find it is always dead in the morning, disconnect one of the battery terminal connectors after you shut the car off.  Then wait the approximate amount of time before the vehicle would normally not start (like overnight). Then reconnect the terminal and attempt to start the car. If the car doesn’t crank and start up as expected, then it’s likely that something in the car is discharging the battery. If not, the battery is discharging itself and it’s time to replace it. Further troubleshooting to find the problem with the car can be exhausting and frustrating if it’s not something obvious or something you suspect.
    3. Your battery is not being charged properly by your car. Alternators typically wear out after 80,000 miles, and most die before they hit 120,000 miles. If your car has to be jumped every time to start it, then the battery is so weak that it can’t hold enough charge to start the car just minutes after turning the car off, or something is wrong in the charging system, most likely the alternator.
      1. This method requires a volt meter, the next method does not but is very dangerous and could lead to serious harm to you and or your vehicle if you don’t know what you’re doing. With your engine running, measure the voltage across your battery terminals with the engine running.  If the voltage is above 13.5, that is a good sign. Reving the engine should not cause a change of more than a volt. However, when you turn the engine off, the voltage should fall below the point it was at when the engine was running (typically between 12 and 13 volts)
      2. This method does not require a meter BUT IS DANGEROUS TO YOU AND YOUR CAR and is not recommended.  While the car is running, disconnect the negative side of the battery, a ” – ” mark and usually a black wire, NOT THE RED ONE ” + ” (for safety reasons). If the engine continues to run, then it is likely that the charging system works and it’s probably time to replace your battery.

It’s important to note that intermittent or weak connections can make diagnosis difficult as sometimes everything works fine and other times it doesn’t.  The older your car is, the more likely that connection problems can exist. Alternators can sometimes produce a half power condition where they produce enough power to run the engine without a battery connected (once started) but not enough power to properly charge the battery.  This is usually a problem with the regulator or, alternator brushes that are about to go out and are making a intermittent connection but rapidly.

Finally, a bad regulator in your alternator can sometimes result in drastic overcharging of your battery which can utterly kill the battery within days. Boiling over of the battery and a rotten egg smell (toxic) can sometimes accompany this condition.

We sincerely hope this information is useful to you.  If you have any comments, please feel free to make them.

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