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Porsche 911 Carrera Alternator Replacement
 
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Pelican Technical Article:

Porsche 911 Carrera Alternator Replacement

Time:

4 hours4 hrs

Tab:

$400

Talent:

**

Tools:

Socket set

Applicable Models:

 
Porsche 996 Carrera models (1999-05)
Porsche 996 Turbo, GT2, GT3 (2001-05)
Porsche 997 Carrera models (2005-08)
Porsche 997 Turbo, GT2, GT3 (2007-08)

Parts Required:

New alternator, new drive belt

Hot Tip:

Tap the inside bushing to release it from the bracket

Performance Gain:

Consistent charging output

Complementary Modification:

Replace drive belts

One of the nice things about the configuration of the Carrera engine is the relative ease with which you can replace the alternator. The alternator is nestled neatly on the left side of the engine compartment and is fairly easy to get at. The replacement and repair process is straightforward and should take you about an afternoon to complete.

The first thing that you need to do is to make sure that your alternator is indeed the cause of the problems with your charging system. Sometimes bizarre electrical problems can be caused by a number of faults other than the alternator. It's important to troubleshoot the system prior to replacing your alternator.

If it seems to be the culprit, check the belt that drives the alternator. Is it tight and amply turning the alternator pulley? If it's worn or close to breaking, then replace it and recheck the alternator (see Pelican Technical Article: Replacing Belts on the Porsche 911 Carrera). Modern belts seldom break, but they get brittle and glazed with age and can slip on their pulleys.

The next item to check is the voltage at the battery. This should read a little more than 12 volts with the engine off. With the engine running at 2000 rpm, the voltage should read at in the range of 13 to 14.5 volts. If your battery appears to be leaking, then your alternator's voltage regulator has probably failed. The battery will usually only leak acid if it has been overcharged at a much higher voltage. If the voltage measured at the battery is more than 16 or 17 volts when the engine is running, then the regulator is probably bad. If your battery has boiled over and has acid overflowing out the top, make sure that you clean up any spilled acid immediately. Dousing the area with a water and baking soda solution should help considerably to neutralize the acid and prevent it from eating away at the metal. Be sure to wear gloves and eye protection.

An important item to check on your car is the engine ground strap. The engine is electrically isolated from the chassis by rubber motor mounts. If the engine ground strap is missing or disconnected, then you might have a whole bunch of problems, including electrical system malfunctions and difficultly turning over the starter. See Project 81 for the exact location of this ground strap.

Before starting any work, make sure that you disconnect the battery. The positive battery terminal is directly connected to the alternator, and it can be dangerous to work on if it's live (see Pelican Technical Article: Porsche 911 Carrera Battery Replacement Trickle Charger Installation).

The first step in removing the alternator is to remove the airbox from the car. Please refer to Pelican Technical Article: Replacing Your Porsche Carrera Air Filter (996/997), Replacing your air filter. Once the air filter is removed, you will need to remove the serpentine belt that drives the alternator. Refer to Project 5 for detailed instructions on the belt removal. You may also need to remove the vacuum connection for the brake booster directly above the alternator for additional space. This is held in place with two 8mm screws. Remove the screws and carefully set the check valve off to the side.

Now, loosen but do not remove the lower alternator bolt, then loosen the idler pulley that is located next to the alternator. Loosen the bolt and back it out about 3-4 full turns. Then, using a drift and a hammer, tap on the bolt. The purpose for doing this is to loosen up the metal bushing that is located inside the rear flange of the alternator. With the bushing loose, lift up on the idler pulley, and the alternator assembly should rotate counter-clockwise. Remove the lower bolt, and the alternator should be able to be lifted up and out of the engine.

On this particular car, the bushing was a tight fit and required quite a bit of tapping, and quite a bit of wiggling to remove. Specifically, I had to use a very long drift to tap directly on the rear bushing to get the assembly loose. Other mechanics seem to indicate that this is a common problem, so you might have to work at it a bit to get your alternator out.

With the alternator unbolted, disconnect the electrical connections from the rear. Reminder: Don't touch these connections while the battery is still hooked up (Pelican Technical Article: Porsche 911 Carrera Battery Replacement Trickle Charger Installation).

If you are replacing the alternator completely, then the installation of the new alternator is simply the reverse of the removal process. Make sure that you reconnect all of the wires to their proper terminals when you are done. If you're still not sure if your alternator is bad, you can take it to any good auto parts store, and they should be able to test it for you for a modest fee.

Shown here is a brand new rebuilt alternator.
Figure 1

Shown here is a brand new rebuilt alternator. Unlike older-style Porsche alternators, this one is pretty much plug-and-play. The regulator is internal, and the alternator should come with the proper pulley installed on the front. The green arrow in the inset photo shows the metal bushing that may give you trouble when you try to remove the alternator. This bushing is the one that needs to be tapped on in order to loosen the assembly for removal.

Shown here are the two 15mm mounting bolts for the alternator on a Carrera engine.
Figure 2

Shown here are the two 15mm mounting bolts for the alternator on a Carrera engine. You'll need to first loosen and remove the upper bolt (green arrow), and back it out about 3 or 4 full turns. Then, using a drift and a hammer, tap on the bolt. The purpose for doing this is to loosen up the metal bushing that is located inside the rear flange of the alternator. With the bushing loose, lift up on the idler pulley, and the alternator assembly should rotate counter-clockwise. Now remove the lower bolt (purple arrow).

On the 996 engines, remove the two 8mm screws (green arrows) holding the brake booster vacuum connection to the left (driver's) side intake.
Figure 3

On the 996 engines, remove the two 8mm screws (green arrows) holding the brake booster vacuum connection to the left (driver's) side intake. This will allow a little more wiggle room to remove the alternator from the engine compartment.

Rotate the alternator to remove it from the engine.
Figure 4

Rotate the alternator to remove it from the engine. It may take a bit of maneuvering to remove, but it is possible. The insert photo shows the brake vacuum line on the 997 engines (green arrow). You can disconnect it from the cross member to give you addition room.

With the alternator unbolted, disconnect the electrical connections from the rear.
Figure 5

With the alternator unbolted, disconnect the electrical connections from the rear. Reminder: don't touch these connections while the battery is still hooked up.

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Comments and Suggestions:
MAC Comments: Nick I have some problems with my 1999 996. Background: Troubleshooting told me my alternator was dead. I couldn't get the $^%#%& thing out. I tried for quite a long time to turn and wiggle the alternator but I just couldn't get it out. So after rereading Jackdflash's comment, I removed the bracket/coolant cover p/n 996.101.215.9R and indeed get a rush of coolant, but the alternator slid right out. Problems: 1 Jackdflash mentioned there was a metal gasket. I didn't see one and wonder is there a replacement gasket available? 2 I broke the tips off a connector on the rubber hose coming off the bracket/coolant cover p/n 996.106.225.51. I've ordered a replacement, but I'm not sure if I need to replace the hoses because the old tip might still be inside the hose. In any case I need to loosen the clips to install the new connector. How do I loosen the clamps that have on spreader? 3 I also broke the brittle small hoses coming off of the changeover value p/n 993.605.123.00. I think I can order the value and the hoses, my problem is it possible to attach the hoses to the other end? Can this be done without dropping the engine. Thanks, MAC
October 8, 2016
  Followup from the Pelican Staff: 1. There is a gasket for that part.

2. In the old hose, remove the broken piece the same way you would remove it.

3. Spreader? Can you share a photo?

4. Get a new valve if broken, then use a vacuum line connector to piece the hoses back together, to avoid major disassembly.


Give The Pelican Parts parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.
- Nick at Pelican Parts
 
Jackdflash Comments: I struggled for a couple of hours trying to remove my alternator following your guide. My car is an early 2005 with a 150A alternator. I finally removed the alternator bracket. Behind that bracket is coolant but you only lose about a quart. The gasket is metal, be careful when moving the alternator to loosen the cable not to snag the gasket and damage it. Otherwise, the gasket does not need to be replaced. Once I decided to remove the bracket the job was straightforward and easy. I too had slow cranking when hot. After replacing the battery the starter showed a lot of power but over time, about a month, slowed more and more. Troubleshooting showed a low charge but not low enough to ever show a warning message. Replacing the regulator solved my problem and the improvement was immediate. BTY I got error messages and "Check Engine" after this work. Stay calm, drive the car around the block, shut it off, start it up, maybe three times, error messages were cleared.
October 1, 2016
  Followup from the Pelican Staff: Thanks for sharing your installation process and experience. These type of comments add so much to the Pelican tech community.
- Nick at Pelican Parts
 
Robert Comments: Removed my alternator today, following these exact steps. Started using an unfastener spray on graphite basis a couple of days back, to help loosen the two alternator bolts. They came off in a jiffy. It's really worth it to take your time to loosen the bolts. When returning the alternator, make sure you don't overtighten the long bolt. This can damage the alternator housing. Anyways, the refurbished alternator makes a difference, with a solid 14v on a cold start, and a drop to just about 13,5v with radio, lights and A/C on. Usefull thing to do, not that difficult at all.
September 9, 2016
  Followup from the Pelican Staff: Thanks for sharing your installation process and experience. These type of comments add so much to the Pelican tech community.
- Nick at Pelican Parts
 
Aly Comments: I thought I would make a post here and ask if anyone has had the "check battery or generator" warning message displayed on the tach for a 997? I have a 2006 911S that had an engine transplant before I bought the car. It had a 2008 Targa 911S engine installed and I believe that is when the warning message began. I have had the battery checked with a battery load tester and the alternator voltage checked which is 13.9 volts. Other than the message that comes up when the ignition key is turned on, the car is fine. I get a P0621 Generator lamp/terminal circuit code under DME on my iCarsoft Porsche II tester that cannot be cleared and status is current. I found info on planet-9.com site that seems to be the cause, a wire change from the DME of blue wire from C-19 to B-12 that was made on these engines after 2006. Here is a link to the forum that outlines the problem that I made a post on.

http://www.planet-9.com/987-cayman-and-boxster-problems-and-complaints/39475-warning-battery-generator-help.html

I did not know if this was the right place to post this, but it seemed relevant. Anyone had this problem corrected?
June 27, 2016
  Followup from the Pelican Staff: Thanks for sharing your repair process and experience. These type of comments add so much to the Pelican tech community.
- Nick at Pelican Parts
 
Zig1999 Comments: In your pictures of the two bolts I broke the mount the lower bolt is in that has a hose coming off of it. purple arrow in you picWhat is this part called and could advise if you carry it?
June 1, 2016
  Followup from the Pelican Staff: That is the alternator bracket. Pelican parts can get you the part.

Give The Pelican Parts parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.
- Nick at Pelican Parts
 
ed Comments: Hi Wayne, Thanks for all your tips. Seems on the forums that a common problem is the cable from the alternator to the starter causing the slow crank when hot that Jeff mentioned also. My '99 is having this issue. Is replacing the cable accomplished by removing the alternator?
February 2, 2016
  Followup from the Pelican Staff: Yes, then follow the cable to starter / battery and replace. - Nick at Pelican Parts  
Jeff Diffenderfer Comments: Removal worked just fine. Thanks.
Alternator check out OK at test. Trouble restarting warm car. Acts like a bad electrical connection and clicks/slow rev with starter or no turnover at all. Checked ground straps. All OK. Where does the battery cable go? Is there another terminal where corrosion could be causing this issue? Thanks. Jeff
January 4, 2016
  Followup from the Pelican Staff: Sounds to me like a faulty battery cable or connection. I would voltage drop test the cables to the starter and engine. - Nick at Pelican Parts  
KK Comments: Hi Wayne. I'm working on this and in process of removing alternator I broke one of the tiny hoses going into pierburg pa6-gf30 just below that brake booster vacuum connection. That hose goes into some netherworld area deep into ? So I just used a bunch of electrical tape good to 220 degrees F and taped tubing together. Best I can do. Does that seem reasonable?
October 20, 2015
  Followup from the Pelican Staff: No, you will have to get in there and replace the hose or component it goes to, if broken. - Nick at Pelican Parts  

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