What's new
Porsche 911 UK Enthusiasts Online Community Discussion Forum GB

Welcome to the @Porsche911UK website. Register a free account today to become a member! Sign up is quick and easy, then you can view, participate in topics and posts across the site that covers all things Porsche.

Already registered and looking to recovery your account, select 'login in' and then the 'forget your password' option.

Welcome to Hartech, the UK's leading Independent Porsche engine specialists, located in Bolton, UK

Latest Fault!! Volt gauge fluctuating - A/C display flashing

thecarfixer said:
That voltage reg is toast. Possibly diode(s) too as there's loads of fluctuation so you're probably hitting everything with AC.

I wouldn't run that until fixed!
Click to expand...

Yes, looking at the video it does look like the rectifier is possibly fubared too, you need to test what AC ripple is coming out of the alternator, should be below 100mv AC. It might just be the voltage regulator though and the control units are protesting on overvoltage.

Multimeter on AC setting, black lead to chassis, red lead on B+ alternator post is best, but battery + Post will show most of the ripple, but dampened by the battery, less than 100mv but 50mv is normal.

I`m thinking more and more that this is your rough running issue Chris :thumb:
 
infrasilver said:
infrasilver said:
Could the pump be affected by the power spikes? The car ran fine tonight until the A/C unit started flashing, the engine stutters and the fans (interior and engine cooling bay) also fluctuate all in turn?
Click to expand...

deMort said:
You have an electrical surgeing fault so it seems .. very strange but easy to prove .. remove the wiring from the alternator .. tape the hell out of the main power lead as you are in a world of pain if that shorts out .

Then run the car .. it wil be on the battery only .. if the fault persists then its not the alternator .
Click to expand...
Click to expand...

very difficult for me to say .. ive not seen anything like this before so i have no real guidance ..

i still think .. you have a battery so a surgeing alternator charge rate if that is what it is would not drop the voltage below battery lvl and as such would have no bearing on the hesitation fault .

If it was a voltage fault then why are there not fault codes for pretty much every control unit .. they all need a set voltage and will generate a code if its too low .

You also have comunication between control units .. again no codes so im afraid im not convinced its the alternator .

I would be more inclined to think a battery lead or an earth lead if we are tying this hesitation fault into the a/c fault .

just replaceing the voltage reg doesnt prove its an alternator . diode pack for a start is what im thinking , this wont be replaced .. hence a disconnect of the alternator would actually prove its that or not .

Over all .. i have no answers im afraid so you would logically start by ruleing out an alternator fault then move on .

Hopefully im wrong and this is the fault though .
 
I was also thinking positive and negative leads and while I have the alternator off for the regulator I will also be cleaning and checking all the leads, I'm also going to change the bearings in the idler pulleys too while the belt is off, a lot of work to do tomorrow. I did once have an battery earth lead break/corrode and this caused the car not to start, once I fixed (bodged) the lead I was able to drive it although it didn't run well but did get me back to the hotel that night where I did a better fix.

As this seems to be intermittent its not going to be easy to pinpoint, the only thing is it does seem to be getting worse so hopefully it does this when I get the car back to my garage and not fry anything on the 3 mile drive.
 
I managed to get the new regulator fitted to the alternator today and initially I was worried about driving the car beforehand, I didn't get any power surging but the gauge was reading around 14.5 volts, maybe a little high but as it didn't surge I was happy it wasn't doing any further damage. I didn't get chance at the time to put the meter on it but I would have expected just under 16 volts going by what I found below.

When I pulled the regulator the brushes were quite worn but I'm unsure as to what point these become totally worn out.

45828022305_8b45c7949e_z.jpg


I refitted the alternator and started the engine, I think it is better but I didn't have a chance to test drive it. I did let it run up to temperature and was seeing just under 14v on the dash and 15.07 on my meter.

46018919914_29531015a5_z.jpg


46018922374_eeef1c2c26_z.jpg


So when the fans kicked in I had all the lights on full including mains and fogs also had the A/C and heated rear window running too.

It dropped to around 14.5 on my meter and just over 13v on the dash. I had no fluctuating of the lights or the engine stuttering. I'm crossing my fingers that this is cured but as we know things are never that simple.

I did also pull all the positive and negative leads and connections and cleaned them all up, they were all in good condition already and I can't see any corrosion of any of the connections or cables.

One question, where are the diodes located ar they in the regulator or another part of the alternator, just thinking ahead if this didn't cure the voltage surging problem?
 
Depends on the type of alternator Chris, looking at what you have there I would say it is a combined voltage regulator/rectifier(diode) unit, were there any other black plastic modules in the alternator after you took the rear cover off ?
Do you have a photo of the back of your alternator ?
 
Scrub what I just said, they are seperate on Bosch alternators, the rectifier ( diode pack ) should look something like this :


ZDoDwBc.jpg
 
Did the engine surging and the flashing of the A/C unit go away ?
 
kurlykris said:
Did the engine surging and the flashing of the A/C unit go away ?
Click to expand...

It did, I think, but as I explained it didn't do it again on the drive to my garage either, (before I fitted it) which was good because it didn't potentially damage anything but bad because it seems to be intermittent and because of that I'm now still unsure if its fixed or not. Although the readings are lower than before and they are more consistent too?

Next question..... where the hell can I buy a rectifier, just searched the net but nothing crops up, apart from a similar part for an Opel??
 
The one in Kris' picture looks similar, the one listed in your link Alex looks totally different even though it says it's for the 996 alternator?

I have the Porsche part number for my alternator 996.603.012.02 and the equivalent Bosch part number being 0124515073 but being unsure of the specification of the rectifier I need to match the above so I think I'll pull the alternator again tomorrow and remove the rectifier to make sure I get the correct part. Again like the regulator there are many parts that are the same or similar and will fit but I want to be 100% for this part.
 
From memory the 996 alternator is more or less identical to one for a VAG 1.9 tdi 150 bhp. The pulley's probably different but I bet electrically they're the same. The regulator I used was a Bosch one for a Skoda. I expect the diode pack is similarly interchangeable. Don't take any of the above as read, but might be a starting point for a search and comparison on eBay?
 
I spent more than an hour trying to match the part numbers with compatible parts and the ones that are supposed to be correct don't match the alternator and the reason I will strip it down again this afto to see what actual part is in there.
 
I removed the alternator again today to get to the rectifier and found it can't be removed with just screws, you need to de-solder the joints around the edge and not wanting to do that without a replacement in hand I put it back together.

46754156811_94d439c7eb_c.jpg


I did find out what the Bosch part number was though. FMOOM133271, there will also be a few compatible parts that will also fit.

31813042907_f4545c5047_c.jpg


I took the car for a 40 miles trip with the lights on and I didn't get the voltage surge or any wavering of the dash lights or gauges, I'm reasonably confident the regulator has sorted this problem out......I think?
 
You must log in or register to reply here.

Similar threads

M
993 Headlight leveller not working
Replies
4
Views
430
guards red
G
Alex
Tensioner Pulley left me stranded in the South of France!
2
Replies
29
Views
3K
Roast Beef Racing
Roast Beef Racing
R
For Sale 996.2 C4 manual Coupe for sale
Replies
6
Views
2K
roofdown
R
D
Locked out of car - found the problem - how to fix?
2
Replies
29
Views
4K
dt4
D
infrasilver
Rough running and stalling. ABS/PSM lights. NOT MAF?
Replies
5
Views
695
Alex
Alex
Porsche News
Plan to push back MOTs to every two years shelved by government
Replies
5
Views
607
Alex
Alex
Y
955 Turbo rear wishbone replacement issue.
Replies
5
Views
383
YPVS
Y
Used Performance Porsche Specialists

Latest posts

New Threads

Porsche Model Range

Porsche 911

Porsche 992: 2018- Porsche 992: 2018- Porsche 991: 2011-2019 Porsche 991: 2011-2019 Porsche 997: 2004-2012 Porsche 997: 2004-2012 Porsche 996: 1997-2005 Porsche 996: 1997-2005 Porsche 993: 1993-1998 Porsche 993: 1993-1998 Porsche 964: 1989-1993 Porsche 964: 1989-1993 Porsche Carrera 3.2: 1983-1989 Porsche Carrera 3.2: 1983-1989 Porsche Carrera SC: 1977-1983 Porsche Carrera SC: 1977-1983 Porsche 930 Turbo: 1975-1989 Porsche 930 Turbo: 1975-1989 Porsche Early 911: 1964-1977 Porsche Early 911: 1964-1977

Porsche Hypercars

Porsche 918 Spyder Porsche 918 Spyder Porsche Carrera GT Porsche Carrera GT Porsche GT1 Porsche GT1 Porsche 959 Porsche 959

Other Current Porsche Model

Porsche Taycan : (2019-0%) Porsche Taycan : (2019-0%) Porsche Macan : 2013- Porsche Macan : 2013- Porsche Panamera : 2009- Porsche Panamera : 2009- Porsche Cayman: 2005- Porsche Cayman: 2005- Porsche Cayenne: 2003- Porsche Cayenne: 2003- Porsche Boxster: 1997- Porsche Boxster: 1997-

Porsche Legacy Models

Porsche 928 Porsche 928 Porsche 968 Porsche 968 Porsche 944 Porsche 944 Porsche 924 Porsche 924 Porsche 914 Porsche 914 Porsche 912 Porsche 912 Porsche 904 Porsche 904 Porsche 550 Porsche 550 Porsche 356 Speedster Porsche 356 Speedster Porsche 356 Porsche 356

Forum statistics

Threads
124,532
Messages
1,441,238
Members
48,944
Latest member
Spider69

porsche insurance porsche parts porsche sales porsche car sales porsche for sale
porsche classic sales porsche tuning porsche sold porsche specialist porsche engine rebuilds porsche driver training porsche car sales porsche exhausts

Community platform by XenForo® © 2010-2024 XenForo Ltd. XenForo theme by xenfocus

www.911uk.com @Porsche911UK THE DEFINITIVE PORSCHE FORUM Copyright © 911UK 2002-2024 All rights reserved.

911uk.com is not associated and is wholly independent of Porsche Automobil Holdings SE, Dr. Ing.h.c.F.Porsche AG, Porsche Cars GB, its subsidiaries and offical Porsche centres. Any word, phrase or graphic that in any way resembles anything to do with the Porsche name or organisation are registered trademarks of Porsche Automobil Holdings SE and Dr. Ing.h.c.F. Porsche AG.

Back
Top