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Discussion Starter #1
So a while ago my battery light came on and eventually I had to replace the alternator which fixed the problem. After about 4 months my battery light started coming on again after driving about 45 minutes of driving on the highway, when I rev the engine it goes off again and if it stop and restart the car it goes off too. The alternator is pretty new and I’ve had it and the battery tested (All good) so I wanna say it’s not either of them. I think it could be the voltage regulator but I’m not sure. anybody have any suggestions? Thanks in advance
 

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2001 Forester
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Connect a volt meter to battery while the engine is running with everything else turned off, what voltage? Connect volt meter with engine off, what voltage you get.

Engine running should be 13.5-14+ volts. Engine off should be at least 12.4 volts.



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Discussion Starter #3
Okay I have done that I get 14.2 with the car off and 15 with the car on. Anything else I could check?
 

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G'day & welcome @Jordantsmart
"normally" those voltages are too high. 14.2 is usual with the vehicle running / 15 is too high with the vehicle running. So, yes, the regulator which is a part of the alternator may be bad.

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Discussion Starter #5
Hi Kevin,
so I got o reillys to replace the alternator under warranty and I placed it into the car. it seems like it was working well for a few days until I was driving in the mountains and the battery light came back on. Do you have any suggestions as to what is going on with my car now? the light is still going on and off but it's much more constant now after driving a few hours in the mountains
 

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@Jordantsmart Could you pls complete your profile so we know what vehicle is involved here; thanks
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Discussion Starter #7
2009 Subaru Forester
X Premium - H4 - 2.5L 2458cc GAS MFI type EJ253 - 4 valve SOHC

Please let me know if I can provide any other information that may be helpful. The alternator I put in was ultima brand
 

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Discussion Starter #11
Probably like 2 hours while I replaced the alternator then I drove to buy the multi meter and checked it
 

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Discussion Starter #15
Yes I am and I have no idea what is could be caused from if you have any suggestions? I’ve replaced the alternator twice now
 

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2007 Forester Sports XT 4EAT
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@Jordantsmart the alternator... battery monitor circuit is pretty basic. I believe it will light on a low charge (low voltage) & a high charge (high voltage) condition. Have you measured the battery voltage when that light is on?

Bobby...
542921

['07 FSXT Member Journal] ['03 X Member Journal]
 

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Discussion Starter #18
So I tired to check it during the battery light and since it’s only while my rpm is over around 3,000 i can’t check it during the light is on. But I did notice while I was driving at night that the head lights, cabin lights, and led clock dim while that light is on. And it’s not a solid light on or a solid dim it’s more of a flicker for both the battery light and the lights dimming
 

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Check the grounds from the battery terminal (you may have done that) and the grounding wires on the engine. Makes me wonder when you say you notice at 3K rpm. It’s just a guess.
lou cioccio
 

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An idea, not necessarily the solution.
 
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