14 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHAlternator
Leading reported evidence
Install only a year
Performed · outcome unconfirmed
No successful repair reported for this finding.
0
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0
Unsuccessful attempts
1
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Performed · outcome unconfirmed
This 997 one that I�m currently using has been installed for only a year, so we�ll see how long it lasts.
Leading evidence: 'Install only a year' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, the most frequently mentioned possible cause is 'ecu can compensate easily' (1 discussions; 0 report identifying it and 1 suggest it). The most frequently discussed action is 'Install only a year' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Performed · outcome unconfirmed
I replaced the cable when I still had the 996 alternator, but it didn�t change a thing.
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Performed · outcome unconfirmed
My voltage fluctuated just like yours until I replaced the starter/alternator cable.
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Suspected cause
more than likely the ecu can compensate easily for that but could be momentary idle instability/jump like when turning on the a/c.
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Suggestion
I replaced the cable when I still had the 996 alternator, but it didn�t change a thing.
Counts describe captured discussions, not unique people or a diagnosis. Author identities are not reliably stored. Exact duplicate evidence is counted once across matching discussions; one discussion counts at most once per action/state. Multiple repairs reported together remain a combination. Suggestions and failed attempts do not establish a fix. Matches cover whole discussions and can include related faults, model variants and incomplete threads.
14 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
Rennlist: 1 discussions
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0 acknowledgements have no verified action link; they do not establish a repair result.
Generation: 20261026T174436Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
Upgrade to the 997 alternator with 150 amps. and direct fit.
997 Alternator AL0815N
Amazon.com: BOSCH AL0815N Original Equipment New Alternator - Compatible with Select Porsche 911, Boxster; 150 Amp : Automotive
Amazon.com: BOSCH AL0815N Original Equipment New Alternator - Compatible with Select Porsche 911, Boxster; 150 Amp : Automotive
I did not know about the 997 route three years ago, but I can tell you that the rebuilt Bosch I bought in 2022 developed bearing problems three years later. I replaced it with a NEW Bosch alternator and it is working better that the rebuilt. Also my Indy says his experience with the rebuilt Bosch is not good.
Wouldn't think so at normal levels.
I'll play the devils advocate....
When/if full amps (150) are requested/required if added electrical accessories/amps/media centers/lights/etc, need the extra amps, it will take more HP to run that alternator.
Also not sure if the existing wiring/fuses can take a continuous 150 amp draw..? Probably not a problem.
The question comes to mind of why.? Does the 997 upgrade do anything other than increase the amp capacity, is it a more dependable unit, bigger bearings, larger slip ring/brushes, better regulator..?
Does the 996 really need a higher amp output alternator...?
Playing Devils advocate again...
from my past M E studies, thought it was '1hp for every 25 amps' on that era automotive Alternator.
But whats more important, at idle speed m96 engine is only generating 5 hp iirr, thats why the idle bump(hp increase) when a/c is on. Now a v8, 10-15hp depending on displacement.
So to produce the extra amps at idle would be a 20% hp @ idle increase needed. more than likely the ecu can compensate easily for that but could be momentary idle instability/jump like when turning on the a/c.
Now this would only happen if the alt was requiring max amp output at idle. Probably never happen unless something like a huge amp and sub were installed and being listened to at idle speed. We've all heard those guys at stop lights blasting tunes/vibrating subs. Thats what I'm talking about maybe along with other current hogging devices, in that case could probably use the extra amps...
Ask again, why..? Is the 997 alt really an upgrade for normal 996 cars ?,,, why scrub even a little HP for what benefit..? Somebody school me on the why...
Electrical engineer stands corrected by M.E. 30 amps X 13V = 390 watts. 750 watts = 1hp. I didn't consider the mechanical and heat loss from generating the extra 390 watts, but if the alternator is 50% efficient, then yeah, it could be a whole hp or maybe more.
With the 997 alternator, my cluster shows a stable 13.9V with the occasional drop to 13.5V. It�s radically different than my experience with the 996 unit, where it�s 14.0V at startup and constantly fluctuates between 12.7-13.5V when warmed up.
I don�t have an upgraded stereo. I do charge my phone and power an external GPS unit, though.
I purchased a 996 alternator rebuilt by Bosch and it lasted only 2 years. This 997 one that I�m currently using has been installed for only a year, so we�ll see how long it lasts. It�s also from Bosch,
but I can�t recall whether it was a rebuilt as well.
edit: my 997 alternator is also rebuilt by Bosch.
My voltage fluctuated just like yours until I replaced the starter/alternator cable. With a new alternator (not rebuilt), new starter/alternator cable and new battery, my voltmeter is pretty much just north of 14V all the time.
The 996 by itself does not need the 997 alternator.
I have a 997 alternator due to all the extras I have inside my car.
Valentine1
Aftermarket radio
GPS (for track app)
Garmin GPS (Second map)
Multiple USB powered GoPros
GMRS Radio for Rallys
Cellphone chargers
