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Alternator repair - Regulator replacement

Low Charge Voltage Problem

Symptoms
Voltage Gauge on dash reading low. It was OK when starting from cold, reading 14 volts, but voltage would drop as engine warmed up, eventually dropping as low as 11.2 volts.

Finding the problem
Measured battery voltage to make sure this was a charging problem and not a gauge issue. This confirmed that battery voltage was low and dash gauge was reading correctly.
Interestingly at a constant speed on the freeway with the voltage at 11.4 volts I could get the voltage to start creeping back up to 11.8 volts by opening the rear spoiler which presumably brought cool air in to bring the alternator temperature down.
My suspicion was the voltage regulator built into the alternator reducing the voltage as it got hot.

Finding a voltage regulator
Through various sources I found and confirmed that the Bosch number for the regulator in the Porsche alternator is F-00M-145-225. It would appear that this part isnít actually listed anywhere as a separate item, although I did manage to track one down on e-bay. All is not lost though, as the same part is available under different part numbers. Various websites cross reference the above part number with the regulator for various Volkswagens from the similar years as well as Audiís and Mercedes. For reference a commonly available part seems to be the F-00M-145-350 or F-00M-145-341 for VW, Audi, and Mercedes which fit perfectly.

These sites reference the different part numbers and various companies offer a replacement part for the Bosch part. These companies usually only have one part number and list ALL the Bosch numbers as equivalents. Here are a few of several possible sources of information. I would like to suggest that you google the part numbers yourself to double check. I have satisfied myself but I cannot guarantee 100%. I can tell you that my car is behaving perfectly with the F 00M 145 350 part.

(Ref; http://www.woodauto.com/Component.aspx?Ref=VRG46473
OR
http://www.mercedesshop.com/shopforum/archive/index.php/t-187174.html
OR
http://www.jnelectric.com/bombridge.asp?bomtype=wu&lc=BO&partnumber=F00M1453 50&manufacturer=Bosch&description=Regulator%2C+Ele ctronic )

I suspect that the different vehicle manufacturers insist that Bosch supply parts with a unique part number or that Bosch manufacture identical parts in different locations and assign part numbers to each. If anyone can give me an informed answer to this or if they can tell me if there really is any difference between them I would LOVE to know!

Here is my new selection of Bosch Regulators



Each one in turn, first the 225


The 350 (Also the Mercedes A003 154 53 06)


& the 341
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1987 911 Carrera Coupe - Carmine Red - SOLD :-(
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Old 05-09-2008, 04:20 PM
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Here are the boxes. It might help with finding them or referencing part numbers. There was no box for the 341.






Now I'll explain the repair procedure...
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2002 996 Carrera Coupe - Seal Grey (Daily Driver / Track Car)
1987 911 Carrera Coupe - Carmine Red - SOLD :-(
1998 986 Boxster - Black - SOLD
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Last edited by Aerkuld; 05-09-2008 at 05:55 PM..
Old 05-09-2008, 04:23 PM
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Removing the Alternator
First step is to remove the air box (filter housing). Snap the oil filler neck out of the clip on the airbox. There is one bolt just to the right of the engine cover catch. Remove this with a 13mm socket. The connector for the MAF sensor will need removing and its wire needs to be taken out of the two clips that hold it to the air box. One of these is obvious but the second is slightly harder to get to being hidden on the back right hand corner of the air box. The only other thing to do is to loosen the hose clamp that holds the rubber hose from the air box to the throttle body. Once these items are loose the air box can be lifted out. Tape over the end of the hose on the air box or jam a clean shop towel in the end to stop anything getting in there.





Now you have good access to the engine to loosen the tension on the serpentine belt. There is one tensioner pulley located roughly in the center of the belt layout. This pulley has a hex-head which you will need a 24mm socket to fit. Rotate the bolt in the pulley with a socket in a clockwise direction (I think - you'll soon find out if not) to loosen the tension on the belt. Keep the load on the pulley while removing the now slack belt from the alternator pulley and idler. You can now release the tensioner.



I also found it an advantage to remove the bracket just above the alternator to give me more space to manouver the alternator later.



Next you can loosen the bolts securing the alternator. There are two bolts that need removing. One of these is a long bolt that passes through the idler pulley to the right of the alternator. After passing through the pulley this bolt then goes through the front flange of the alternator, then fits in a long slotted feature which is fixed to the engine before screwing into a threaded bushing which is a press fit into the rear flange of the alternator. This threaded bushing can move in the flange and actually slides forward as you tighten the bolt so that the bushing and the back of the front flange clamp both ends of the long slot to secure the alternator.




You will find later that the threaded bushing needs to be pushed back into the flange in order to refit the alternator. If you are able to push it back in at this point it will also make the alternator easier to remove. To do this you need to loosen the long bolt by three or four turns then give the bolt head some sharp, hard taps with a hammer. It is a good idea to use a wooden block between the bolt head and the hammer. Once you have tapped it back far enough then you can remove this bolt and the second bolt on the left hand side of the alternator. The alternator should be relatively easy to wiggle out part way now so that you can remove the wiring connections on the back. When I did mine I didn’t manage to get the bushing to move and didn’t want to hit the bolt too hard and risk breaking a flange. It may have worked if I was to take the whole bolt out and soaking the threaded bushing with penetrating oil before refitting the bolt and trying again. As it was I managed to get the alternator loose by gently levering it up free of the clamping faces.
With the alternator part way out you can remove the plug on the back. It has a little catch that needs to be released before pulling it off but it should come off quite easily. Now you can move the alternator out further so that you can remove the nut from the terminal to remove the other wire. With the two wires removed the alternator can be removed from the car.


Last edited by Aerkuld; 05-10-2008 at 08:23 AM..
Old 05-09-2008, 05:33 PM
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If you are in any doubt at this point you could take the alternator to a parts store and get them to check it. HOWEVER, if it is a temperature dependent problem they may say that the alternator is fine as it probably wonít get hot enough on their test equipment to show the fault.

Replacing the regulator

First remove the plastic cover from the end of the alternator. There are two nuts that need to be removed from the threaded terminals and one cross head screw.



Once these are off the cover just pulls off. Now you have access to the regulator itself. There is one small cross head screw which attaches a wire loop connection from the rectifier to the regulator. This needs to be removed along with two longer cross head screws which mount the regulator to the alternator.



With these removed the regulator just slides out sideways.



It is probably a good idea to give the alternator a good clean with some electrical contact cleaner at this point. You can then check the wear on the slip rings and make sure everything else looks in good shape. The new regulator is simple to fit, just be careful sliding the brushes in to the housing as you do not want to damage them. Once in place you just refit the screws and reassemble the end cover. Job done!

Refitting the Alternator

If you didnít manage to get the threaded bushing loose then you will need to do this before you attempt to refit the alternator. If not you will find it impossible to get everything lined up to the point that you can slide the two right hand flanged over the long slotted boss. To move the bushing it will probably help to give it a very good soak with some penetrating oil and fit the long bolt (without the pulley) so that it threads fully into the bushing.

Next you need to find a socket that can fit over the outside diameter of the bushing but still contact the alternator flange. Stand the alternator up on end with the socket under the flange. Find something to support the weight of the alternator so that it sits level on the socket, I used a folded towel. With the alternator sitting square either use a press or a few sharp taps with a hammer to knock the bushing down into the flange. Once the face of the bushing is flush with the face of the flange you should have no problem getting the alternator back in.

Rest the alternator in position so that you can refit the big wire to the terminal stud before refitting and tightening the nut. Make sure itís tight. Refit the plug and push it on until it snaps in place. Wiggle the alternator back in place and refit the long bolt with the pulley now fitted. The long shank of the bolt between the two alternator flanges can be inserted into the slot. While the long bolt is still loose pivot the alternator around until you can fit the short bolt on the left and tighten finger tight.

Now tighten the long bolt to around 40 to 48Nm (30 to 35 lbs-ft). It will need to be sufficiently tight to pull the bushing back into contact with the slotted boss and clamp the alternator in place. You will probably hear a brief Ďcrackí if the bushing moves suddenly Ė donít be alarmed. Make sure it is tight by making sure that you cannot push the alternator bolt up out of its slot. Now tighten the shorter bolt to about 34 to 40Nm (25 to 30 lbs-ft).

Use the 24mm socket to remove the tension on the belt tensioning pulleyagain and refit the serpentine belt over the alternator and idler pulleys.

This might sound stupid but PLEASE DON"T FORGET to remove the tape or shop cloth from the air box hose and refit the air box, tightening the hose clamp and refitting the mounting bolt.

Now put the MAF sensor wire back into both harness clips on the back of the airbox and reconnect the plug.

Finally start the car, allow it to warm up, and check the charge voltage. Like I said up top somewhere, mine is now working perfectly and I have had no issues at all using the F 00M 145 350 regulator.
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2002 996 Carrera Coupe - Seal Grey (Daily Driver / Track Car)
1987 911 Carrera Coupe - Carmine Red - SOLD :-(
1998 986 Boxster - Black - SOLD
1984 944 - Red - SOLD
Old 05-09-2008, 05:43 PM
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I hope this is clear and helpful. It might help to save buying a new or rebuilt alternator. To give you some idea I paid about $80 to have a regulator shipped to me overnight. A rebuilt alternator is about $300, a new Porsche one is listed as being over $1000!
If anyone has any criticism, comments, or anything to add then please let me know.

One other comment on the differences between alternators should you need a new one. There are two different alternators for the 996 and 986 for the early year cars depending on transmission type. The only difference between them is the pulley. The automatic cars have a standard fixed pulley while the six speed cars have a one way roller bearing, or one way clutch, built into the pulley. The one way bearing/clutch works like a freewheel sprocket on a bicycle. On the alternator it will allow the engine to drive the alternator as long as the engine is not rotating slower than the alternator. If the engine speed drops then the alternator will carry on spinning freely until it slows down enough for the drive to resume. I won't go into detail, but this helps to reduce the loads on the drive belt which helps to lengthen belt life. There is a special tool available for $20-30 which allows you to remove the pulleys. You can also buy the pulley seperately, I'll see if I can find the part number and I'll post that.

Obviously I have a few spare regulators now. I will hang on to one of them for myself. If anyone else is looking for one then please PM me. Even if I don't have a spare left I may be able to locate one or suggest where to look.

Last edited by Aerkuld; 05-10-2008 at 08:47 AM..
Old 05-09-2008, 06:00 PM
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Great write-up

You did a wonderful job of explaining in detail and with pictures during DIY Alternator repair including where to get parts. Absolute asset to this site thanks.
Old 05-14-2008, 02:06 PM
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Nice writeup and great pictures! Thanks
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Old 05-15-2008, 08:25 AM
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Thank you very much.....I'll add this to my, very big, "how-to" binder.
Great job,
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Old 05-16-2008, 10:13 AM
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Very nice write-up, indead. I always like it when someone goes an 'unusual' route and saves some bucks in the process. Great job. I have to commend you on taking all these pictures. I ususally get so involved in my projects that I forget to snap them until it is too late....

One comment; I would add in big fat bold letters to disconnect the battery before working on the alternator. The alternator is connected straight to the positive terminal of the battery via a 16mm2 cable without any fuse or relay. If the ring connector touches the engine case it will fling melted metal around.

Ingo
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Old 06-12-2008, 02:36 PM
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Sorry to resurrect a really old thread, but this was really helpful for me. I want to add one bit of caution for anybody replacing their V regulator: When you remove the screws holding the regulator to the alternator body, use lots of pressure. These screws require lots of force to turn them, and you are likely to strip the heads. If you do, getting them out will be a royal pain.
Old 12-23-2010, 02:02 PM
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Thumbs up Thank you

Hi

Just wanted to thank you for your superb DIY on replacing the voltage regulator. I found a link to it in the Porsche Club GB forum.

I had very similar symptoms to those described in your post, so I took the plunge and decided to use your DIY and put a new regulator on. Battery now charging perfectly for the small cost of 24 GBP instead of a new alternator and a big garage bill!

Your DIY is excellent, easy to follow with very useful photo's and tips.

Many thanks indeed.http://forums.pelicanparts.com/ultimate/smile.gif

Simon
996 C4
Sheffield
UK
Old 01-11-2012, 11:33 AM
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wow, many thanks for write up.

Last edited by sa321; 03-15-2012 at 12:00 AM..
Old 01-21-2012, 10:41 AM
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Very useful post indeed

Thanks Aerkuld for your truly comprehending post, saved me hundreds of pounds!! With your instructions I think this job is around a 2/10 in terms of difficulty so if anyone is reading this and thinking should I try thins myself I would say go for it. Worth noting that the tension of the fan belt is self adjusting so there is no need to worry about getting this correct. During the job I also noticed a couple of loose bolts and screws on my air box and a missing rubber airbox mount that my Porsche specialist clearly did not care about, needless to say I will not be giving them any further business.
Old 06-23-2012, 03:31 AM
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Indeed a great Article

As of sept. '12 Pelican is getting $37.50 for the Regulator. My '03 c2 had a 145 350 Regulator and new part I got was a 144-136. Same Item. Smooth and simple job. THANKS
Old 09-24-2012, 12:17 PM
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Great detail and photos made this a straightforward task.
I decided to go with a rebuilt alternator. Thanks !
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