Mike 911
New member
[FONT=calibri"]Dear PCGB members,
[FONT=calibri"]Can anyone offer me advice with the following issue?
[FONT=calibri"]
[FONT=calibri"]I went to start my 996 3.4 C2 and the battery was flat, I connected jump leads from another vehicle and it started immediately.
[FONT=calibri"]Once running I put a multimeter across the battery terminals and the reading was 14.5 volts so I assumed the alternator was charging properly?
[FONT=calibri"]The battery was over 9 years old so before doing anything else I fitted a new one, the car started fine, I ran it for a few minutes then turned it off and left it, after two days of sitting in the garage the car would not start, the new battery was flat.
[FONT=calibri"] I removed the battery, recharged it and left it for a few days (off the car), tested the voltage over a few days and the new battery appears to hold charge.
[FONT=calibri"]
[FONT=calibri"]So now I am thinking maybe there was nothing wrong with the old or new battery? and I tried some more tests:
[FONT=calibri"]With the new battery charged and re-fitted I used a multimeter to measure the drain, from cold with the car turned off the reading was around 0.04 Amps (I understand the vehicle can take an hour to ‘shut down’ properly) but from what I have read this reading sounds sensible?
[FONT=calibri"]
[FONT=calibri"]I re-connected the battery and ran the car, as before the reading at the battery terminals was 14.5 volts, but this time I left the car running and as the car came up to temperature the reading at the battery terminals shot up to 17 volts. With the car turned off I again tested the battery drain which was now reading was around 3.35 to 3.90 Amps.
[FONT=calibri"]
[FONT=calibri"]Sounds like an alternator related issue?, [FONT=calibri"]I have read a various information and read things about voltage regulators and diodes etc but most things I have read relate to the alternator undercharging? Mine seem to be over charging when the car is warmed up? And why does the battery discharge but only appears to show the drain on the multimeter when warm? Are these two issues related or one of the same?
[FONT=calibri"]
[FONT=calibri"]Any advice would be really gratefully received, as you can tell from the above I am certainly no expert! I am just trying to understand the basics before looking at my options to repair it; Are my tests sensible/valid, [FONT=calibri"]Any more tests I should try?, should I replace parts? voltage regulator? Are the diodes part of the voltage regulator, can these be replaced etc. Is it false economy or difficult to replace these parts should I go for a new or reconditioned alternator? Right now I am thinking of removing the unit and taking it to an auto electrician, as I say a[FONT=calibri"]ny advice would be really gratefully received.
[FONT=calibri"]Thanks in advance []
[FONT=calibri"] [FONT=calibri"]
[FONT=calibri"]Kind regards
[FONT=calibri"]
[FONT=calibri"]Mike
[FONT=calibri"]Can anyone offer me advice with the following issue?
[FONT=calibri"]
[FONT=calibri"]I went to start my 996 3.4 C2 and the battery was flat, I connected jump leads from another vehicle and it started immediately.
[FONT=calibri"]Once running I put a multimeter across the battery terminals and the reading was 14.5 volts so I assumed the alternator was charging properly?
[FONT=calibri"]The battery was over 9 years old so before doing anything else I fitted a new one, the car started fine, I ran it for a few minutes then turned it off and left it, after two days of sitting in the garage the car would not start, the new battery was flat.
[FONT=calibri"] I removed the battery, recharged it and left it for a few days (off the car), tested the voltage over a few days and the new battery appears to hold charge.
[FONT=calibri"]
[FONT=calibri"]So now I am thinking maybe there was nothing wrong with the old or new battery? and I tried some more tests:
[FONT=calibri"]With the new battery charged and re-fitted I used a multimeter to measure the drain, from cold with the car turned off the reading was around 0.04 Amps (I understand the vehicle can take an hour to ‘shut down’ properly) but from what I have read this reading sounds sensible?
[FONT=calibri"]
[FONT=calibri"]I re-connected the battery and ran the car, as before the reading at the battery terminals was 14.5 volts, but this time I left the car running and as the car came up to temperature the reading at the battery terminals shot up to 17 volts. With the car turned off I again tested the battery drain which was now reading was around 3.35 to 3.90 Amps.
[FONT=calibri"]
[FONT=calibri"]Sounds like an alternator related issue?, [FONT=calibri"]I have read a various information and read things about voltage regulators and diodes etc but most things I have read relate to the alternator undercharging? Mine seem to be over charging when the car is warmed up? And why does the battery discharge but only appears to show the drain on the multimeter when warm? Are these two issues related or one of the same?
[FONT=calibri"]
[FONT=calibri"]Any advice would be really gratefully received, as you can tell from the above I am certainly no expert! I am just trying to understand the basics before looking at my options to repair it; Are my tests sensible/valid, [FONT=calibri"]Any more tests I should try?, should I replace parts? voltage regulator? Are the diodes part of the voltage regulator, can these be replaced etc. Is it false economy or difficult to replace these parts should I go for a new or reconditioned alternator? Right now I am thinking of removing the unit and taking it to an auto electrician, as I say a[FONT=calibri"]ny advice would be really gratefully received.
[FONT=calibri"]Thanks in advance []
[FONT=calibri"] [FONT=calibri"]
[FONT=calibri"]Kind regards
[FONT=calibri"]
[FONT=calibri"]Mike