# 09 Miata-something draining battery



## Ronnie1a (Aug 1, 2007)

I can only go 5-6 days before the battery on my Miata goes dead. Now on 3rd battery. Had it to dealer 2x and an auto electric shop 1x. They claim nothing is draining the battery. The elect. shop did not even charge me and the dealer says I just don't drive it enough. If I do not drive it for a week or so I have to put a trickle charger on it so I can start it.

Any thoughts on what it might be? Is this a common problem with this car?


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## PoleCat (Sep 2, 2009)

I have had the same problem with certain vehicles. I blamed the diodes in the rectifier for leaking excessively.


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## Windows on Wash (Aug 30, 2011)

Leave it at the dealership. In no way shape or form is 5 to 6 days and acceptable amount of time to kill a battery. This is a car issue and if they can't figure it out you can lemon law the car.


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## danpik (Sep 11, 2011)

The easiest way on some older cars to find the current leak is to unhook the battery ground cable and connect a volt meter between the battery and the cable. With the key off you will see a voltage measurement show up on the meter. Pull one fuse at a time until you see it drop. This may or may not work on the newer cars as there are some systems that draw current even with the car off. Might be worth a try though. If you do not have a meter, a simple test light can be used to. It will light up if something is drawing current and go out when you pull the fuse on the circuit causing the problem. Do not try to start the car or turn the key on during this test


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## 47_47 (Sep 11, 2007)

Newer cars are similar to newer smart phones. Both have a lot of extras always running and will drain a battery, even when not in use. Dan's method will work, but you need to know what is a normal parasitic load for your car.

How much do you drive the car after you get it running and do you fully charge the battery before you drive or just enough to start it? I would fully charge the battery, let it sit for the few days and try it.


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## GrayHair (Apr 9, 2015)

Years ago I had a Ford van same problem and mechanics told me the same thing. Turned out to be the ignition switch intermittently shorting. I found it by doing what danpik suggested, but *you must configure your meter to read current* (amps). You should also have spare fuses on hand for the meter.

Start on the highest current scale available (fuse protection) and start pulling fuses, noting which ones cause current to increase when removed; omit these fuses during further testing. Change to the next lower scale and do it all again. 

I had to go through all my tests several times and ended up having someone watch the meter while I thumped with a rubber mallet and slammed doors. I actually located the bad ignition switch while pounding on the dashboard with my fist. :furious:

Stick with it and you will most likely find it. :thumbsup:


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## Brainbucket (Mar 30, 2015)

I just get a 12 volt test light. I disconnect the neg cable from battery and 'jump' it with the test light. 1 end on bat, other on neg cable. Start pulling fuses and replacing 1 at a time and watch for test light to go dimmer or off. Record which fuse made light dimmer. Sometimes it's more than 1 fuse. If it starts flashing, that means a module is trying to 'go to sleep'. Wait a few minutes untill the flashing goes away or pull fuse to stop it. If it won't go to sleep, take note as that could be it. If that doesn't work, look at the main power grid to find that which is not fused but has a fuse link, ie, alternator. I've had a few bad alt's sapping power. easy way of finding that is take off alt belt and try to turn alt with key on. It should turn freely. If sapping power it should be real hard to turn if at all and you should hear a humming noise coming from it. Once you find the fuse that makes the test light go out, go to system wiring diagram on that fuse circuit and start disconnecting each component untill light goes out. Sounds hard but it isn't. By the way a good charging voltage is 13.5 to 14.5 in general. Good luck.


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