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alex yates
Fuji


Joined: 06 Mar 2014
Posts: 9703
Location: Lancashire

2000 Porsche 996 Carrera 4

PostPosted: Tue Feb 28, 2017 8:53 pm    Post subject: Low volt reading after start-up Reply with quote

Noticed a few times recently that after a cold (morning) start-up, my volt meter is reading low, as though there's no juice coming from the alternator. After around 30 seconds, it springs into life and jumps up to the normal 14ish volts.

Convinced it's not the belt slipping or anything to do with the alternator not spinning. Do think though it's something to do with moisture on the armature or something similar.

Any ideas members?

Caught it (not) in action this morning setting off to work.


Open Youtube Page

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2000 Manual 996 C4 Arctic Silver Convertible

 
  
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mzmini
Suzuka


Joined: 30 Jan 2015
Posts: 1064
Location: Somerset


PostPosted: Tue Feb 28, 2017 9:04 pm    Post subject: Reply with quote

Hi Alex just been reading something about this sound as if a diode or 2 a playing up

http://www.knowyourparts.com/technical-articles/starters-and-alternators-common-misdiagnosis/
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Storm996
Nürburgring


Joined: 03 Jul 2013
Posts: 475



PostPosted: Tue Feb 28, 2017 10:47 pm    Post subject: Reply with quote

If you have a multimeter (even a cheapo one will do) then leave it in the car.

Connect it to the cigarette lighter socket just before you start it. When it shows low on the needle see what the multimeter says.

Then you can compare actual volts with the needle.
 
  
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alex yates
Fuji


Joined: 06 Mar 2014
Posts: 9703
Location: Lancashire

2000 Porsche 996 Carrera 4

PostPosted: Tue Feb 28, 2017 11:46 pm    Post subject: Reply with quote

Thanks for the comments guys. Will keep my eye on it and try the multimeter in the fag lighter trick.
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johnca58
Newbie


Joined: 07 Dec 2016
Posts: 2



PostPosted: Wed Mar 01, 2017 8:46 am    Post subject: Reply with quote

Some over on this side of the water seem to think there may be a delay charging built into the regulator of about 4-5 seconds, not 30s. here is the post.

http://rennlist.com/forums/996-forum/977091-delayed-charging.html
 
  
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arry
Montreal


Joined: 02 May 2015
Posts: 538
Location: South Essex


PostPosted: Wed Mar 01, 2017 9:11 am    Post subject: Reply with quote

This is what's currently laying my 996 up. New battery, new alternator, 13.6 at the posts when running but showing sub 12v on the instrument cluster. Disco warning lights and flickering gauges, and stalls on occasion as soon as the brake lights are illuminated, at which point it won't restart despite it having 12v+ at battery.

It seems charging issues such as this are common.
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Demort
Magny-Cours


Joined: 21 Mar 2015
Posts: 2536
Location: Sussex


PostPosted: Wed Mar 01, 2017 9:30 pm    Post subject: Reply with quote

Try an alternator load test ..

Turn on all electrical items , main beam , fog lights etc etc and test the charge rate with a meter at the battery , if under 13 volts then the alternator is starting to fail , if over then it is ok .

This might be just the gauge in the cluster , they are only an indication really ( Porsche had a gap to fill in the cluster lol ) so not 100% accurate and if it wasnt charging then you should have had a battery light or warning message depending on the system your car has displayed .
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coopertrooper2001
Silverstone


Joined: 07 Oct 2013
Posts: 141



PostPosted: Wed Mar 01, 2017 10:24 pm    Post subject: Had this problem Reply with quote

Had this exact same issue a few times over the past 3-4 months. Did it most reliably after rain or on cold mornings. I also had a slight shriek noise on start up, like a belt slip.

Had it into Northway and they said it could be the alternator packing up. I specified a new belt and it has not done it for the past month since I collected the car.
 
  
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kurlykris
Albert Park


Joined: 30 Jun 2014
Posts: 1645
Location: Warwickshire


PostPosted: Wed Mar 01, 2017 10:28 pm    Post subject: Reply with quote

Sounds like damp getting into the Voltage regulator/rectifier to me Alex, quickly drying off when it warms up. Not too bad a job to swap the regulator/rectifier by the looks of things on youtube Thumb

Mine is straight to 14V after firing up Grin
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wasz
Barcelona


Joined: 28 Dec 2012
Posts: 1487


1999 Porsche 996 Carrera 2

PostPosted: Sun Mar 19, 2017 6:59 pm    Post subject: Re: Had this problem Reply with quote

coopertrooper2001 wrote:
Had this exact same issue a few times over the past 3-4 months. Did it most reliably after rain or on cold mornings. I also had a slight shriek noise on start up, like a belt slip.


Mine is doing this now.

startup- 10.5v, then after a few seconds, a shreik from the back and up to 14v.

Did anyone get to the bottom of this?

Going to remove the belt and check all pulleys spin.
 
  
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Demort
Magny-Cours


Joined: 21 Mar 2015
Posts: 2536
Location: Sussex


PostPosted: Sun Mar 19, 2017 7:30 pm    Post subject: Reply with quote

Theres another post which not the same but has a similar fault which turned out to be the ignition switch ..

http://911uk.com/viewtopic.php?t=112115&postdays=0&postorder=asc&start=0

Not sure if its relevant here but it wasn,t really what i was expecting for his symptoms .

i think if theres a noticable screetch from the rear then the alternator is faulty as thats the belt slipping or alternator not turning when first started .

Worth takeing off the belt and checking the alternator spins freely as well as the other pullys .
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Shane911
Newbie


Joined: 07 Dec 2016
Posts: 24



PostPosted: Sun Mar 19, 2017 7:33 pm    Post subject: Reply with quote

Dirty earth strap Very Happy
 
  
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Demort
Magny-Cours


Joined: 21 Mar 2015
Posts: 2536
Location: Sussex


PostPosted: Sun Mar 19, 2017 7:37 pm    Post subject: Reply with quote

Shane911 wrote:
Dirty earth strap Very Happy


Floor

I just read that post Very Happy

Not sure about the misfire bit , coils i expect .. think im going to have to start checking these more often .. Question
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wasz
Barcelona


Joined: 28 Dec 2012
Posts: 1487


1999 Porsche 996 Carrera 2

PostPosted: Sun Mar 19, 2017 7:57 pm    Post subject: Reply with quote

Just been to the car, but it went dark on me so I didn't remove the belt.

Engine started: 10.5v on the dash

ran to back of car opened lid

looking at the pulley it is spinning looks OK

then "shreik" and a puff of smoke from the alternator pulley location

dash now reading just under 14v

----strange

I was reading about the alternators (exciting) and manual 996 2000 on started coming with clutched freewheeling pulleys, as the belts were jumping off on fixed pulley manual cars with abrupt rev changes.

Now mines an MY99 so would have shipped with a fixed pulley but it may have had an alternator in 128k miles.

Could it just be the clutch in the pulley thats gone perhaps?

Belt looks fine, doesn't look like its been slipping.
 
  
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Harv
Österreich


Joined: 18 Sep 2014
Posts: 929



PostPosted: Sun Mar 19, 2017 8:43 pm    Post subject: Reply with quote

Does sound as though the clutch in your alternator pulley is failing and slips a bit before sorting itself out.

I'd remove the drive belt and try turning it by hand. It should be locked and turn the alternator when you turn it in the direction of normal running rotation and then if you abruptly stop it the alternator shaft and internals will free wheel.

It's not an expensive part

http://www.ebay.co.uk/itm/INA-Replacement-Freewheel-Clutch-Alternator-535002510-/192043159037?fits=Car+Make%3APorsche%7CPlat_Gen%3A996&hash=item2cb6aa0dfd:g:XH4AAOSw-RFYsfEW

Could also be a worn out drive belt or failing tensioner, all easily inspectable while your in there testing the alt pulley.

Good luck

Thumb
 
  
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DynoMike
Suzuka


Joined: 25 May 2012
Posts: 1160
Location: The Cotswolds

2003 Porsche 996 Turbo

PostPosted: Sun Mar 19, 2017 10:26 pm    Post subject: Reply with quote

It's just the wet belt slipping imo. Mine did it before and after a new alternator but only after rain or washing the car. It has done exactly the same thing for the last five years so it doesn't me me a jot.
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Pickse
Spa-Francorchamps


Joined: 20 Jul 2013
Posts: 260
Location: Fleet, Hants


PostPosted: Mon Mar 20, 2017 7:35 pm    Post subject: Reply with quote

DynoMike wrote:
It's just the wet belt slipping imo. Mine did it before and after a new alternator but only after rain or washing the car. It has done exactly the same thing for the last five years so it doesn't me me a jot.


Mine also did this before and after a new alternator was fitted.
I hadn't yet made the connection with rain or water.
I'll try and be more observant.
What I do know is it wasn't the alternator that needed changing Sad
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2003 Arctic Silver 996 Turbo Tiptronic S
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DynoMike
Suzuka


Joined: 25 May 2012
Posts: 1160
Location: The Cotswolds

2003 Porsche 996 Turbo

PostPosted: Mon Mar 20, 2017 7:50 pm    Post subject: Reply with quote

Pickse wrote:
DynoMike wrote:
It's just the wet belt slipping imo. Mine did it before and after a new alternator but only after rain or washing the car. It has done exactly the same thing for the last five years so it doesn't me me a jot.

What I do know is it wasn't the alternator that needed changing Sad


Question Tell us more! On second thoughts if it is bad, perhaps not wack

Grin
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wasz
Barcelona


Joined: 28 Dec 2012
Posts: 1487


1999 Porsche 996 Carrera 2

PostPosted: Mon Mar 20, 2017 7:52 pm    Post subject: Reply with quote

Ok so I looked again at the alternator.

I have a fixed pulley so it may be the original.

Car fired up today and 14v straightaway.

Promise I will take the belt off tomorrow and check for free movement of pulleys and tensioners.....

If I find nothing amiss I will monitor and then put it down to a damp belt. Got a new belt and water pump waiting to go on when it ever stops raining.
 
  
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DynoMike
Suzuka


Joined: 25 May 2012
Posts: 1160
Location: The Cotswolds

2003 Porsche 996 Turbo

PostPosted: Mon Mar 20, 2017 8:20 pm    Post subject: Reply with quote

wasz, mine does it with a new belt or an old one. 100% only happens when the car has been washed or stood in heavy rain, on most occasions I can hear a squeel as the belt grips and starts charging.

It is worse after washing due to the car shampoo I use, I think. It is slippery stuff!
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