Mazda MX-5 Battery Draining Diagnosis

 

If your Mazda MX-5’s battery is draining, it’s something that’ll need addressing right away.  If it is draining while your MX-5 is off, it’s usually caused by something that is drawing current that shouldn’t be.  If the battery is draining while you’re driving, that is probably going to be the alternator or battery.  There are other situations as well.  We’ll cover those for you below.

 

Battery Draining Mazda MX-5

 

Mazda MX-5:  Battery Draining While Parked

If your vehicle is running fine when you park it, and it won’t start, there could be a few problems causing this to happen.  Most of the time, it’s the battery itself causing this problem.

 

Battery Cables

You’ll want to take a look at your MX-5’s battery posts where they bolt to the battery.  If there is a lot of corrosion here, you’re going to want to clean that off with a wire brush.  There are also specific battery post cleaners that you can buy.  They are usually less than 10 bucks at the local parts store or Wal-Mart.  

 

Bad Battery

When the battery drains when parked, the odds are that it’s the battery itself.  If your MX-5’s battery light came on while you were driving, but before you parked, it could be the alternator.  If you didn’t see a battery light, and now the vehicle is dead when you go to start it, the first thing that you need to look at is the battery.

You can take it up to the local parts store and have it tested.  They’ll need to charge it for a while, so plan on dropping it off and returning a few hours later.  They’ll tell you if it holds a charge or not.  If it passes the test, it’s time to move on to the alternator.

 

Alternator

It is possible that the alternator wasn’t charging the battery enough when the vehicle was running and has left the battery drained.  Most parts stores can test an alternator for you.  They usually don’t charge anything for this service, they just want to sell you an alternator if you need it.

 

Mazda MX-5 Battery Draining

 

MX-5 Battery Draining While Parked

If your MX-5’s battery is draining after being parked for a few days, here are two possible scenarios.

  1. The battery itself has gone bad and just can’t hold a charge long enough to be of any use after the vehicle sits, and it drains.
  2. Something is drawing power when it shouldn’t be.  If this is the case, the first thing that you are going to want to look at is all of the lights.  If your MX-5 is equipped with a glove compartment light, check and see if it is turning off.  Maybe one of the map lights is on?  How about all of the accessory plugs?  Is something plugged into one of them and drawing power?  Any aftermarket accessories?  If not, it may be that there is an electrical problem.

Here’s a pretty good video on exactly how to track down a “parasitic draw”.

 

Battery Draining While Driving:  Mazda MX-5

If your battery is draining while driving, it is almost without exception the MX-5’s alternator that is causing the problem.  If it is you should see the battery or alternator light on, it indicates that the alternator is not creating the necessary voltage to charge the battery.

It could be a bad battery, or more likely a bad battery cable too.  But it’s not very likely.  If you hear a whining noise accompanied by the battery light, it’s almost guaranteed that it’s the alternator that is at fault.

 

Conclusion:  MX-5’s Battery Draining

Good luck running down what is causing your battery to drain in your Mazda MX-5.  If there is anything you would like to add, please feel free to leave a comment below.

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