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Random Battery Failure Experience

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Old 03-12-2017, 12:08 PM   #61
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Before you replace anything be sure and do all the system check via the videos posted. Here another check you might want to try.

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Old 03-12-2017, 09:21 PM   #62
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Yeah I put multimeter to the battery main posts/leads for testing purposes. My findings were as follows, after having driven the car for about 20 minutes or so at varying speeds:

Engine off - 12V
Engine on, idling - 12.9V
Engine on, headlight on, idling - 13.1V
Engine on, headlight on, revs held @ 2500RPM - 13.2V

Pretty sure at this point it's the voltage regulator, but I might as well change the entire alternator while I'm at it. Currently window-shopping for cheapest Bosch 150A one.
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Old 03-12-2017, 09:29 PM   #63
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Quote:
Originally Posted by mfanatic325 View Post
Yeah I put multimeter to the battery main posts/leads for testing purposes. My findings were as follows, after having driven the car for about 20 minutes or so at varying speeds:

Engine off - 12V
Engine on, idling - 12.9V
Engine on, headlight on, idling - 13.1V
Engine on, headlight on, revs held @ 2500RPM - 13.2V

Pretty sure at this point it's the voltage regulator, but I might as well change the entire alternator while I'm at it. Currently window-shopping for cheapest Bosch 150A one.
You should check to see if you have a parasitic current draw before replacing anything. You may have a bad control module or other electrical short drawing current overnight. This is very easy to check.
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Old 03-12-2017, 09:43 PM   #64
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I'll check it by bridging the gap as mentioned in the video, and see if there's any draw. If there is, then I'll start pulling fuses to try and pinpoint the parasite
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Old 03-12-2017, 10:42 PM   #65
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So I hooked up my ammeter as instructed in the video, and using the DC Amp mode, found around -3 Amps draw with car sitting unlocked, key out of ignition, no lights on.

I then started pulling the fuses one by one to try and find one with significant change, and the only obvious one was B1, which accordig to the fuse diagram is: "Cluster Tiptronic Button PSM Diagnosis Power Top".
My car is a 6spd manual, coupe, so the only thing in that description that is of any eaning to me is PSM? No idea what it could be. But pulling that fuse lowers the draw from
About -3Amps to -2Amps.

All other fuses were tough to tell when pulled, due to the varying nature of the readings.
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Old 03-12-2017, 10:54 PM   #66
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So I hooked up my ammeter as instructed in the video, and using the DC Amp mode, found around -3 Amps draw with car sitting unlocked, key out of ignition, no lights on.

I then started pulling the fuses one by one to try and find one with significant change, and the only obvious one was B1, which accordig to the fuse diagram is: "Cluster Tiptronic Button PSM Diagnosis Power Top".
My car is a 6spd manual, coupe, so the only thing in that description that is of any eaning to me is PSM? No idea what it could be. But pulling that fuse lowers the draw from
About -3Amps to -2Amps.

All other fuses were tough to tell when pulled, due to the varying nature of the readings.
The car should have a normal draw in the 40-60 mA range when the car is fully powered down (everything off, then wait about 5 min. or so), anything beyond that is a problem. I would start looking for any aftermarket installs (radar detector, phone charger, iPod, etc.) that is connected to an "always hot" circuit like the cig lighter.

If you do not find any aftermarket devices, you then need to start checking the OEM stuff one at a time as they sometimes also can crap out and start an unexpected drain.
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Old 03-13-2017, 02:39 AM   #67
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There are no aftermarket electronics devices that I know of that I can think of off the top of my head that could draw 2 Amps of power. Factory alarm, factory radio, etc.
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Old 03-13-2017, 10:43 AM   #68
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Your ignition switch may be the cause. Try fiddling with it as you check for power draws.
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Old 03-13-2017, 05:24 PM   #69
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Will look into it, thanks.
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Old 03-17-2017, 11:20 PM   #70
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I had problems with batteries on my 996 NA and 996 TT. Walmart has a nice trickle charger for $10. Hook it up every time car is parked and cured the problem-car is used about once a week

Be sure hood is clicked down-otherwise a light will say in in the engine compartment-you can see it on through the the vents..
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Old 03-17-2017, 11:35 PM   #71
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I've gone ahead and ordered a new alternator, which will come with new voltage regulator (cost about $250). Labor to install it will be $200 through Porsche master tech.

The most recent voltage measures through my handheld voltmeter (with engine running as well as not-running) has convinced me that at the very least, that the voltage regulator is on its way out, and is not properly charging the car while the engine is running. And since I'm going to pay for the labor to get in there anyways, might as well replace the entire alternator too at the same time.

If for whatever reason there's still a draw after alternator swap, then I'll look into replacing the ignition switch. Will have master tech check the draw on anything else he can find, while the car is in the shop.

Will report back in a week or two
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Old 03-18-2017, 12:07 PM   #72
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I've gone ahead and ordered a new alternator, which will come with new voltage regulator (cost about $250). Labor to install it will be $200 through Porsche master tech.
those are great prices. i think i paid 600! and i dont "overpay" for very much lol. sounds like a "reman" bosch price, but even if so.. it'll work.

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since I'm going to pay for the labor to get in there anyways, might as well replace the entire alternator too at the same time.
exactly. a wise decision. solid bet your issue will be fixed.
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Old 03-22-2017, 12:04 AM   #73
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New alternator installed. Voltages measured around high-13s even with headlights on. So far so good. Will report back if overnight draw issue persists. But I think the voltage regulator within the alternator was ultimately the culprit, and am hoping that this is the end of it all

I'll look into getting my old alternator rebuilt, and see if anyone on the forum needs a rebuilt one, or else I keep it for myself as a spare or something.
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Old 03-22-2017, 10:10 PM   #74
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while you may see 14 regularly while its brand new, it'll settle after a bit down to 13 under full load. some things about these cars are fairly predictable.
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Old 03-22-2017, 10:32 PM   #75
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while you may see 14 regularly while its brand new, it'll settle after a bit down to 13 under full load. some things about these cars are fairly predictable.
Right now it's just under 14V with engine running. I went for a 30-minute drive throughout the neighboring cities and the voltmeter on the dash didn't really fluctuate much during the drive.
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