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Discussion Starter #1
We are on a second battery in 2 years - had my mechanic test out the system and he said the battery was dead but alternator was ok. I went to S__Rs to get my battery replaced under warranty and the alternator test failed with "Bad Waveform - Replace Alternator". Could this have been my problem all along? Maybe the alternator is killing the battery (the second one showed 4 V under load). The counter guy at S__Rs said to get a second opinion. I want to install a B15 alternator but don't know who to believe...
 

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looking for a can opener
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bad batteries give bad test results when doing a charging/starting test. Hopefully they were smart enough to test the alternator after replacing the battery. But anyway, it could just be a coincidence the the alternator went in between the time
 

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Easy to test yourself. With the engine running you should see 13.5-13.8 volts at the battery. Use a cheap multimeter. If you see this voltage then the alternator is probably OK. If you see a voltage lower than 13 volts or higher than 14 volts then the alternator is bad.

Battery should show 11.8-12.5 volts with the engine off.

Two years is too short for a battery. Something is not right. Make sure your cables are in good condition with clean ends and battery posts.
 

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Discussion Starter #5
i had two batteries die before one year was up over the past two years. the last one was barely a year old and had been flaking out since spring. they tested the alternator after they put a new battery in at S__Rs, that's when they got the "bad waveform" read. my mechanic had put a new battery in and tested it (passed) but i refused the battery since the old one was still under warranty being less than a year old. last year my started died and he had checked the electrics back then too. i will have another re-test on friday on my mechanic's tester...
 

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Discussion Starter #6
i brought it to an automotive electrical specialist (starters, alternators, batteries). he showed me that under load (with lights on etc), my voltage dropped from 14.4 to 12.3. he installed a new alternator and when he showed me the same test it sustained 14.2. $190 installed for a new alternator - not bad in this day and age! the wrench had the hardest time - had to take of the engine mount, fan, cooling hose. i guess he never worked on a g20 before...
 

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Pizdeet kak Trotsky
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Its annoying when the ancillaries start acting up :(

Good to hear your sorted :beard:
 

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jsmith said:
i brought it to an automotive electrical specialist (starters, alternators, batteries). he showed me that under load (with lights on etc), my voltage dropped from 14.4 to 12.3. he installed a new alternator and when he showed me the same test it sustained 14.2. $190 installed for a new alternator - not bad in this day and age! the wrench had the hardest time - had to take of the engine mount, fan, cooling hose. i guess he never worked on a g20 before...
Glad you got your car fixed.

I've been told several times that battery voltage drop under load is normal.

Is it normal or not?
 

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Pizdeet kak Trotsky
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jj94auto said:
I've been told several times that battery voltage drop under load is normal.
Is it normal or not?
The batt voltage will drop under load .......... However if the motor is running to at least 2K rpm it shouldn't drop below 13.8v

In theory ....... I spose as long as it don't drop below 12v ya will be ok
 

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Discussion Starter #10
i would hate to find out that's normal, although i would tend to doubt it. maybe that big a drop is not good as that would mean that the battery basically wasn't charging (even discharging) when i had my headlights on. also the oscilloscope "bad waveform" diagnosis was a prior check that it had flunked...
 

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Pizdeet kak Trotsky
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jsmith said:
i would hate to find out that's normal, although i would tend to doubt it. maybe that big a drop is not good as that would mean that the battery basically wasn't charging (even discharging) when i had my headlights on. also the oscilloscope "bad waveform" diagnosis was a prior check that it had flunked...
Well if ya charge rate goes below 12v the batt is bound to crap out innit
 

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Very good information
 
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