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Helpful ReplyDIY - Alternator Voltage Regulator replacement

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MarkGolf
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2020/12/17 11:41:02 (permalink)

DIY - Alternator Voltage Regulator replacement

In light of wanting to add more DIY's, to save you guys money and get you a bit more hands on, a small and failing common failing point of the 964 is the voltage regulator.

You can take 2 hours if you go about this the long way, removing HT leads, pulleys, removing the fan/alternator etc etc but I am going to tell you the quick way, 20-30 mins. 
 
Symptoms: Weak voltage upon first starting, car had to be revved a number of times to get the voltage up. My car died on me due to the battery voltage being drained due to insufficient charge. Upon investigation, I discovered the alternator to not be charging the battery.

Buy a voltage regulator, many choices out there, I went for Beru as a known and good make. £20 from eBay.
 
You will need
 
Philips screwdriver
10mm socket
A mix of hex sockets/keys (Can't recall the size)
 
That's all! 
 
Disconnect your battery!
 
Open decklid to expose your wonderful masterpiece of an engine.
 


Remove the 2 hex bolts retaining your HT lead cover in place and let this hang down in front of the fan

Loosen the 3 mm bolts from the air duct that sits just behind the HT leads



Undo the long hex bolt from the fan retaining bracket


The fan assembly should pull toward you now, giving you enough access to the rear, where you will find a black cover. This has 4 10mm nuts holding it on, undo these and remove, this will expose the rear of the alternator. 
 
Peer around and you will see the voltage regulator, this is held in with 2 philips screws. 
 
Old Vs New, old appears to look ok but clearly wasn't.


Remove these screws, the screw driver will not be dead straight, so be careful not to round the screwheads if mega tight. Once undo, the voltage reg will be free to pull and replace with your new one. Due to the new brushes, it will take a small amount of jigging around to get it in but it's not hard. 
 

 
That's it, now reverse what you have done to refit, button up and test! 
 

 
You should see over 14v on the battery when running at idle. ideally 12.80v when car off, may dip down to 10-11v when cranking. With lights, fans you may see 13.8v.

Hope this helps
post edited by MarkGolf - 2020/12/17 13:38:52

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18 Replies

mcgc0
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Re: DIY - Alternator Voltage Regulator replacement 2020/12/17 12:38:44 (permalink)
This is an excellent Christmas break mini to-do project. Nice one Mark. I know I need to replace the battery some point - over 6 years old now and was dumb enough to let it drain completely for a few weeks (forgot to switch on the CETEK). Not been the same since. I also have a theory that maybe, just maybe, a replacement reg will resolve a PDAS dash light normally caused with a low voltage being detected at the alt (<8.5v). Doesn't affect PDAS in any way as a throttle blip to 3k rpm clears the lights. This is the Beru GER004 part, yes?
 
Marcus

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MarkGolf
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Re: DIY - Alternator Voltage Regulator replacement 2020/12/17 12:46:38 (permalink)
Hi Marcus,
 
It's funny, I was randomly seeing my ABS light upon starting the car and it would disappear after a blip of the throttle, since fitting this, no more! 
 
That's the part number! 
 
Really simple job, while youre in there, just check the condition of the contacts on the alternator shaft, they could be worn/damaged. 

Current fleet
1991 964 Carrera
2005 997 Carrera S
2008 957 Cayenne GTS
2003 Boxster 2.7
1994 Eunos Roadster S Special Turbo 270bhp!
1991 Mercedes 500SL
1979 Mercedes 280e
1995 VW Golf VR6 3.0
mcgc0
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Re: DIY - Alternator Voltage Regulator replacement 2020/12/17 18:16:32 (permalink)
Will do Mark. I will also take meter voltage readings, as I've done in the past, with the alternator under different load conditions (i.e. incl all lights, heater etc at idle and again at 2k rpm). Will do this before and after reg replacement. I had some Porsche baseline readings somewhere - can't remember where from, will have to have a look.
 
Yes, the ABS+PDAS lights staying on from start up isn't uncommon. Once wound up to 3k lights go out and stay out (even back at idle). Only when ignition turned off/on again does it reoccur. I know that under normal driving the voltage reading increases so all good. I've had this for 5-6 years without any problems. Would be interesting to find out if it is down to the dicky regulator.
 
Added to my to-do list with the front diff swap out (once I've fitted new seals to the cheap one I found on ebay).

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mcgc0
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Re: DIY - Alternator Voltage Regulator replacement 2020/12/17 18:18:40 (permalink)
Why is one mounting hole in the new reg reinforced and the other isn't?

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MarkGolf
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Re: DIY - Alternator Voltage Regulator replacement 2020/12/18 09:28:32 (permalink)
Diff swap will be fun! 
 
Yeah, I was messing around with the car last night and I was consistently getting the ABS light but now, nothing, the reg has definitely sorted that for me. 
 
No idea on why one is reinforced, I would have said it looks like one fell out but they're both the same, no idea!

Current fleet
1991 964 Carrera
2005 997 Carrera S
2008 957 Cayenne GTS
2003 Boxster 2.7
1994 Eunos Roadster S Special Turbo 270bhp!
1991 Mercedes 500SL
1979 Mercedes 280e
1995 VW Golf VR6 3.0
mcgc0
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Re: DIY - Alternator Voltage Regulator replacement 2020/12/18 11:58:14 (permalink)
MarkGolf
No idea on why one is reinforced, I would have said it looks like one fell out but they're both the same, no idea!



Have one turning up in the next day or two. Genuine Beru for £15 delivered! All the places I looked showed the reg as having just the one hole reinforced. No matter though.

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AndrewCS
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Re: DIY - Alternator Voltage Regulator replacement 2020/12/18 12:51:32 (permalink)
mcgc0Why is one mounting hole in the new (and old) reg reinforced and the other isn't?

 
Same arrangement as a previous Mk2 Golf ... possibly a `reference` connection to the alternator if the metal is sandwiched in the item ? 
 

Aberdeenshire (R2) : Cayman GT4 981 - Cayman S PDK 981 - Cayman R 987.2


mcgc0
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Re: DIY - Alternator Voltage Regulator replacement 2020/12/18 13:48:17 (permalink)
Interesting, could be. I'm sure it's fine. If I really wanted to I guess I could make my own insert to fit. I'll see.

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vitesse
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Re: DIY - Alternator Voltage Regulator replacement 2020/12/18 14:41:22 (permalink)
I think that is to Earth the regulator & minimise static interference

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mcgc0
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Re: DIY - Alternator Voltage Regulator replacement 2020/12/18 15:17:34 (permalink)
Ah, of course. You're always wiser than I Colin.. :)

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mcgc0
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Re: DIY - Alternator Voltage Regulator replacement 2021/05/23 19:35:22 (permalink)
Hoping for some help;
 
Changed over the voltage regulator - fiddly. Had a major (smoking) problem with connecting new battery - new Bosh battery posts at different ends to the previous type (will explain more later in another post). Question I have is knowing what v readings at the battery I should be expecting from the alternator charging.
 
Before starting the engine the battery gives a steady 12.4v. When starting the engine on idle it drops to 11.9 then over a warming up period of roughly 20+mins there's a slow decline to 11.4. Engine switched off and the battery reading is back to 12.0.
 
I've been suspecting the battery was on it's way out for a while - the car dies after about 500m of driving off (needing to restart and keep revs really high to make it back home).
 
So, would it be a case that the battery just isn't taking the alternator charge output any longer. Should the readings at the battery on engine idle be much more than what I was seeing? Not sure if the battery is done or if the alternator is done and needs replacing.
 
Mark, when you changed your regulator did you check charge readings at the battery.
 
Thanks
 
Marcus

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les richards
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Re: DIY - Alternator Voltage Regulator replacement 2021/05/23 20:30:20 (permalink)
I understood the voltage with engine running should be around 14v.

Les Richards
Essex
5152 MU - 993 Coupe Polar Silver
mcgc0
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Re: DIY - Alternator Voltage Regulator replacement 2021/05/23 20:56:32 (permalink)
les richards
I understood the voltage with engine running should be around 14v.


Yes, I think you're right Les. When I checked a short while ago some readings I took from a previous 964 across a range of constant revs with all electrical items on (lights full beam, fogs, heater, wipers etc), I was getting 13.8 at worse. I was probably forcing myself to believe it was the battery while the devil on my shoulder was telling me it's the alternator.
 
I'll start looking around for a replacement. Although I thought I saw/heard somewhere that there are a few specialists in the Midlands who can re-wire or 'refurb' older alternators. Some homework to do.
 
Annoyed that I swapped one Bosch battery for another without realising that, despite being identical makes and specs, the terminal posts were the 'other side' of the battery and I simply placed it in the same orientation as the previous Bosch one where the clamps are nearest. Wasn't until I touched the clamps that to the posts that smoke started coming from the engine bay - bloody shorted briefly and frazzled the thick brown alternator to crankcase earth cable. Alternator back out again this time to repair and make good that cable. Arghhh...
 
 
post edited by mcgc0 - 2021/05/23 20:58:15

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vitesse
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Re: DIY - Alternator Voltage Regulator replacement 2021/05/24 10:52:51 (permalink)
Marcus -you should definitely be getting over 14 volts at the battery when engine running with reasonable alternator -hope your reverse polarity hasn't done other harm to the ECU etc.

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mcgc0
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Re: DIY - Alternator Voltage Regulator replacement 2021/05/24 11:11:03 (permalink)
Thanks Colin. With the repaired alternator-to-crankcase cable (although thinking about making a dedicated replacement instead in the future), I fired up the engine fine and let it idle for a bit. Assuming if the ECU was damaged then the ignition start and steady idle would have been lost or erratic. Will follow some Steather book and rennlist discussion checks and advice for the alternator this afternoon - trying to rule out any other curve balls or anomalies. If still no change then I guess it's a case of removing the alternator from the fan/housing and send off for an exchange unit or get mine repaired.

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les richards
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Re: DIY - Alternator Voltage Regulator replacement 2021/05/24 14:32:04 (permalink)
...further to my earlier response I dug out my Lidl/Aldi 12v Battery & Alternator Tester - clips across the battery, series of lights - normal sort of thing.
 
It gives typical values thus:
Alternator charge function. 
15.5v overload, faulty regulator
14.5v charging at maximum
13.2v charging OK
Battery condition.
12.6v fully charged
12.0v half charged
11.5v charge very low
 
Might be a wee bit late for you at this stage but it gives useful figures to keep a note somewhere should you have problems in the future.
 

Les Richards
Essex
5152 MU - 993 Coupe Polar Silver
mcgc0
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Re: DIY - Alternator Voltage Regulator replacement 2021/05/25 10:54:34 (permalink)
Thanks Les. I think I'm facing an alternator rebuild whether I like it or not :) I have one more check to do with the battery/alternator warning light that does not come on when ignition switched on (and it should). This is taken from the alt D+ wire and if this isn't working then the alternator does not receive the correct input for a charge state.
 
Spoke to a company that rebuilds alternators for classics and looking at @ £300 all in. Would rather have my original Bosch unit rebuilt rather than a straight swap for a service/remanufactured exchange unit. At least then I will find out what was the exact failure is/was. A tad peeved as I have my MOT booked in tomorrow and had thought of driving there with jump leads, but now thinking too risky if essentially I'm just driving on battery v's..

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mcgc0
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Re: DIY - Alternator Voltage Regulator replacement 2021/07/05 19:19:28 (permalink) ☄ Helpfulby AndrewCS 2021/07/05 19:26:18
Been meaning to post an update for a couple of weeks now.. All good, car running with no problems.
 
Issue: Car normally kept on CTEK conditioner 24/7. Engine started fine but within 15 mins (driving or stationary) would stall and stop altogether. Would not restart without jump leads from another battery/car.
 
Investigation: Assumed that highly likely battery was at fault - no longer keeping charge. Wasted too much time taking all kind of battery load readings under different conditions of electrical equipment on/off without clear consensus (brain hanging on to the idea that the battery must be at fault – or that’s what I’d hoped it would be). Bought new Bosch S4 74Ah battery and eventually got round to fitting this - or trying to. New battery terminal +/- post orientation is the opposite to what the current battery is, meaning cables will not reach now opposite battery posts.
 
Knew I needed to start also thinking the alternator maybe not doing what it is supposed to do. With a fully charged battery on start up the readings across the battery terminals, and from the 12v accessory circuit, would start at 12+v but within couple minutes would gradually drop to 9v. Alternator charge circuit not behaving as it should and car essentially running on battery only. Followed Mark’s advice earlier in this post and swapped out the voltage Regulator for a new Beru one. Made no difference. Resigned myself to having to take an alternator rebuild route – new genuine/OEM replacements ridiculous money £500-£800 in some cases. Classic car alternator rebuild specialist offered a rebuild at £250 +VAT.
 
Carried on looking at other charging circuit issue stories and read more into the technical workings of alternator charge states and trigger signals. One rennlist issue in particular stood out – essentially the alternator not being signalled or initialised on ignition start up. The clock alternator/battery warning light is part of the alternator circuit (probably obvious to most). Not having noticed some of the warning lights weren’t working, or never working in the first place, I assumed as the car was previously running fine then naturally no warning lights would show – a thumbs up. However, it’s the ignition on state that I hadn’t being paying attention to – in my case no warning lights on at all.
 
Turns out the alternator needs the warning light to provide a starting current to ‘ignite’ the alternator field winding. I needed to trace the alternator circuit feed to the warning light, and this is the small/thin D+ blue(ish) cable going into the back of the alternator. With the meter and ignition on I grounded the D+ line at its corresponding pin in the engine bay fuse box plug connector to check if warning light came on or stayed off. It stayed off. Also checked for continuity between the alternator D+ terminal and the same connector pin. No issue there. Everything now pointing downstream towards an issue near the clock.
 
Removed the clock from the dash - what an effort that was! Visual inspection of the gauge plug, cable and the PCB didn’t reveal anything obvious. Removed all warning light lamps and tested these – only a couple not working but the alternator warning lamp fine. De-soldered the PCB from the gauge and removed this to check and test for dry cracks on the underside – all good. Tested between alternator light and its plug pin and all good. Head scratching. PCB lamp slots are numbered 1 to 11 for the warning lights. However, there is another lamp #12 that has no corresponding warning light. As well as this there is a second lamp on the board that has no number ID at all. Both are 1.5w while all the others were <1w. Spent a few minutes tracing these on the PCB and testing at different circuit locations. One of these had gone/blown and this one traces on to the alternator warning light. While the alternator lamp itself was fine there was no supply to it.
 
Fix: Luckily I had a spare rev counter in the garage and removed other 1.2w fuse lamps from this and replaced the dud ones on the clock with these. Ignition on, bingo, alternator (and other warning lights) all on. Some of these other warning lights I’d never seen before! :D like the seat belt light for starters..
 
New fuse lamps bought for @ £1.50 each and when they arrived I swapped these over. So, feel I dodged a bullet big time there if I had left it with a specialist to sort – anything up to £500+ for a new alternator plus loads of investigation hours at £90-£100/hour plus VAT on top. Instead my own time, £3.00 in fuse lamps, an £80 battery I can’t use but many non-working hours of doing my head in.
 
Charging now at a steady 13.8v throughout rev range and with all electrical accessories, lights etc on. Perfect. Summer spirited driving awaits.
 
Hope others can learn from this and save them the aggravation and hassle I went through.
 
Marcus
post edited by mcgc0 - 2021/07/05 19:22:04

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