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Cayman 987 3.4s parasitic battery drain (Alternator ?) - Page 1 - Boxster/Cayman - PistonHeads UK

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5 captured repliesPartial discussion capture · Source accounts, not a confirmed diagnosis

THIS DISCUSSION / SOURCE-DERIVED OVERVIEW

Discussion summary

YOUR RESEARCHCayman 987 3.4s parasitic battery drain (Alternator ?) - Page 1 - Boxster/Cayman - PistonHeads UK

Leading reported evidence

Install alternator due

Performed · outcome unconfirmed

No successful repair reported for this finding.

0
Reported fixes: 0
Unsuccessful attempts: 1
Discussions

Read evidence and context

Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.

Discussions that performed work without a confirmed outcome: 1

0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.

0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.

Performed · outcome unconfirmed
I fitted a new alternator due to the original being over 20 years old but you can buy the diode pack on it’s own
Original post Read captured discussion
Cayman 987 3.4s parasitic battery drain (Alternator ?) - Page 1 - Boxster/Cayman - PistonHeads UK

Frequently discussed work

Check after leaving the car overnight

No successful repair reported for this finding.

0
Reported fixes: 0
Unsuccessful attempts: 1
Discussions

Read evidence and context

Discussions that contain suggestions: 1

0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.

0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.

Suggestion
I used an infra red thermometer as a quick check after leaving the car overnight.
Original post Read captured discussion
Cayman 987 3.4s parasitic battery drain (Alternator ?) - Page 1 - Boxster/Cayman - PistonHeads UK

Read full discussion summary

Leading evidence: 'Install alternator due' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Check after leaving the car overnight' (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.

Source reports, not a diagnosis or a success probability. Counts refer to discussions and can overlap.

Read captured replies

1 matching discussions · 5 captured posts examined · 1 partial discussions

Compare 4 other evidence results

Test seems

Performed · outcome unconfirmed

No successful repair reported for this finding.

0
Reported fixes: 0
Unsuccessful attempts: 1
Discussions

Read evidence and context

Discussions that performed work without a confirmed outcome: 1

0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.

0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.

Performed · outcome unconfirmed · Original poster
New Bosch alternator fitted and tested seems to have done the trick !
Original post Read captured discussion
Cayman 987 3.4s parasitic battery drain (Alternator ?) - Page 1 - Boxster/Cayman - PistonHeads UK

Use infra red thermometer as a quick

Performed · outcome unconfirmed

No successful repair reported for this finding.

0
Reported fixes: 0
Unsuccessful attempts: 1
Discussions

Read evidence and context

Discussions that performed work without a confirmed outcome: 1

0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.

0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.

Performed · outcome unconfirmed
I used an infra red thermometer as a quick check after leaving the car overnight.
Original post Read captured discussion
Cayman 987 3.4s parasitic battery drain (Alternator ?) - Page 1 - Boxster/Cayman - PistonHeads UK

Check after leaving the car overnight

Suggestion or failed attempt

No successful repair reported for this finding.

0
Reported fixes: 0
Unsuccessful attempts: 1
Discussions

Read evidence and context

Discussions that contain suggestions: 1

0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.

0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.

Suggestion
I used an infra red thermometer as a quick check after leaving the car overnight.
Original post Read captured discussion
Cayman 987 3.4s parasitic battery drain (Alternator ?) - Page 1 - Boxster/Cayman - PistonHeads UK

Run battery down if it’s not

Suggestion or failed attempt

No successful repair reported for this finding.

0
Reported fixes: 0
Unsuccessful attempts: 1
Discussions

Read evidence and context

Discussions that contain suggestions: 1

0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.

0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.

Suggestion
That can run the battery down if it’s not used for a few days.
Original post Read captured discussion
Cayman 987 3.4s parasitic battery drain (Alternator ?) - Page 1 - Boxster/Cayman - PistonHeads UK

Frequently discussed actions (6)

These are separate views of the same evidence. Frequency alone does not establish a fix, and these counts must not be added together.

Check after leaving the car overnight

No successful repair reported for this finding.

0
Reported fixes: 0
Unsuccessful attempts: 1
Discussions

Read evidence and context

Discussions that contain suggestions: 1

0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.

0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.

Suggestion
I used an infra red thermometer as a quick check after leaving the car overnight.
Original post Read captured discussion
Cayman 987 3.4s parasitic battery drain (Alternator ?) - Page 1 - Boxster/Cayman - PistonHeads UK

Install alternator due

No successful repair reported for this finding.

0
Reported fixes: 0
Unsuccessful attempts: 1
Discussions

Read evidence and context

Discussions that performed work without a confirmed outcome: 1

0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.

0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.

Performed · outcome unconfirmed
I fitted a new alternator due to the original being over 20 years old but you can buy the diode pack on it’s own
Original post Read captured discussion
Cayman 987 3.4s parasitic battery drain (Alternator ?) - Page 1 - Boxster/Cayman - PistonHeads UK

Run battery down if it’s not

No successful repair reported for this finding.

0
Reported fixes: 0
Unsuccessful attempts: 1
Discussions

Read evidence and context

Discussions that contain suggestions: 1

0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.

0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.

Suggestion
That can run the battery down if it’s not used for a few days.
Original post Read captured discussion
Cayman 987 3.4s parasitic battery drain (Alternator ?) - Page 1 - Boxster/Cayman - PistonHeads UK

Test battery etc

No successful repair reported for this finding.

0
Reported fixes: 0
Unsuccessful attempts: 1
Discussions

Read evidence and context

Discussions that contain suggestions: 1

0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.

0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.

Suggestion · Original poster
My usual Indy (not auto electrician) connected it up to his new bit of equipment to test battery etc.
Original post Read captured discussion
Cayman 987 3.4s parasitic battery drain (Alternator ?) - Page 1 - Boxster/Cayman - PistonHeads UK

Test seems

No successful repair reported for this finding.

0
Reported fixes: 0
Unsuccessful attempts: 1
Discussions

Read evidence and context

Discussions that performed work without a confirmed outcome: 1

0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.

0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.

Performed · outcome unconfirmed · Original poster
New Bosch alternator fitted and tested seems to have done the trick !
Original post Read captured discussion
Cayman 987 3.4s parasitic battery drain (Alternator ?) - Page 1 - Boxster/Cayman - PistonHeads UK

Use infra red thermometer as a quick

No successful repair reported for this finding.

0
Reported fixes: 0
Unsuccessful attempts: 1
Discussions

Read evidence and context

Discussions that performed work without a confirmed outcome: 1

0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.

0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.

Performed · outcome unconfirmed
I used an infra red thermometer as a quick check after leaving the car overnight.
Original post Read captured discussion
Cayman 987 3.4s parasitic battery drain (Alternator ?) - Page 1 - Boxster/Cayman - PistonHeads UK

Coverage and how to read this overview

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.

5 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.

PistonHeads: 1 discussions

0 evidence records excluded for query context · 0 excluded by outcome qualification · 0 adjusted by outcome qualification.

0 acknowledgements have no verified action link; they do not establish a repair result.

Generation: 20261026T183130Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources

POST 1 / ORIGINAL POSTEROriginal post

I am having a bit of bother with this. My battery is draining down overnight, dead as a dodo. My usual Indy (not auto electrician) connected it up to his new bit of equipment to test battery etc. and it showed a slightly lower alternator performance. I then took it to an auto electrician to diagnose and he said it looks like the alternator and described a diode potentially open all the time that leads to the battery draw? He doesn't want to fix it and asked me to take the car away, which cast a bit of doubt over his diagnosis. My question is, Is it possible for an alternator, if faulty, to drain a fully charged battery overnight ?

POST 2Original post

I had this issue on my Boxster and it would drain the battery in 24 hours. I used an infra red thermometer as a quick check after leaving the car overnight. The alternator was noticeably warmer than the surrounding engine components. I fitted a new alternator due to the original being over 20 years old but you can buy the diode pack on it’s own

POST 3Original post

Do you have Porsche Vehicle Tracking System? That can run the battery down if it’s not used for a few days. I now keep my Cayman on a CTEK charger in winter

POST 4Original post

Rethw said: My question is, Is it possible for an alternator, if faulty, to drain a fully charged battery overnight ? In a word, yes. If you are in a position to do this, disconnect the alternator (leave it in place) and see if it solves your problem, if you still have the problem you have saved the money and effort.

POST 5 / ORIGINAL POSTEROriginal post

Thanks for the replies. New Bosch alternator fitted and tested seems to have done the trick !

This is a source reference. Confirm exact model applicability in the original material.