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Help my battery keeps going dead :(   

 

 Just bought a 1999 Legacy and having a few problems. One is I keep loosing charge to my battery. I have purchased and installed a new battery and this did not help.(New battery still goes dead) My alternator is charging around 14V so I am currently looking for some type of drain on the system. I just checked the positive post on my alternator and there is battery voltage to the post with the key in the off position . Could this be the problem?

 

Thanks Bill

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The alternator is directly connected to the battery so it should have power whenever the battery is hooked up. What you need to do is go to an auto parts store and get one of those cheapo battery disconnects. Put it on the negative terminal then take your multimeter and with it set on amps touch both ends of the disconnect. With the multimeter leads touching the disconnect, disconnect the battery and check how much amperage the gauge says. If its any significant amount start by pulling fuses one at a time and redoing the test to see witch one takes away the amperage. That should narrow down the circuit.

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 Went to get the disconnect and had the auto store check my system they said the alternator was bad.

The alt is putting out over 14v but the regulator inside or the diodes are bad. 

 

Thanks for your reply.

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Go to a dealer for the alternator or order from an online dealer.

Those alternators were part of a service bulletin back from 95-99 and Subaru sells them remanufactured for less than auto parts stores. The Subaru remans are much much higher quality. The last one I bought was around $80. They may have gone up some since then.

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I've had that failure a couple of times. One of the rectifier diodes partially fails allowing current to back flow from the battery.

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hello guys im looking for some help with my 91 loyal, something was draining the battery and i started with pulling all the fuses and putting them back in, 1 at a time, and see if it caused a spark when connecting the negative back up, and i found the fuse, its the fuel fuse, and i cant find a wiring diagram to find out where its going, any help would be appreciated thanks. o yeah i for got to mention, 1 side of the fuse box, under the dash is always hot, for the fuel fuse, is this right?

Edited by matthew23

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I'd have to check my fsm. More people with loyales will see your post on the older generation forum, best to start a new thread.

 

The most accurate way to check for sneak current is to disconnect a battery terminal and put a running lamp bulb in series. It will glow depending on how much current is being drawn. Then pull fuses until it goes out. Also pretty common failure is alternator output rectifier. Disconnect the heavy white wire on the back of the alternator to check that one.

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I've had that failure a couple of times. One of the rectifier diodes partially fails allowing current to back flow from the battery.

Thanks daveT i will check that diode next

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It kind of hard to check the diodes directly.  Use your mulitmeter on AC volts, measure at the battery when charging. 

 

If a diode is bad, then you will see lots of AC, even if you are getting 14 V out of the regulator.  Normal AC will be about 50 mV or less. 

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