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      09-29-2014, 06:41 PM   #1
fastgaas
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Replacing Alternator - DIY, fairly easy.

Replaced my alternator this weekend and it took 2 hrs max. Very easy to do on my 2004 2.5 Z4.The alternator started making a loose metal sound and shortly later the battery light came on inside the cabin. I bought a BOSCH rebuilt unit online (Bavarian Autosport) and it was delivered in 2 days. I replaced the belts since it was all off. Probably save yourself $400 in dealership labor. Mine engine is simpler than the 3.0 and turbo I think.

I would highly recommend this as a simple DIY project since I think it would be hard to screw up.

Basic instructions (look at other posts on “belts” for pictures)

1. Remove air intake filter box (two screws and one hose clamp, just unplug sensor)
2. Remove bottom shroud (8 screws or so, easier to access belts from below)
3. Place TORX on spring loaded bottom belt tensioner, leverage over and slide off belt
4. If you will re-use belt, remember orientation
5. Now use a 16mm socket and leverage the upper belt tensioner, slide off belt
6. Unplug Alternator oval connector
7. Remove red main power connector on alternator (I taped it to cover just in case power appeared on it and shorted somehting)
8. Remove dust cap on main pulley
9. Use 16mm socket to remove alternator top bolt and main pulley
10. Use 16 mm socket and remove bottom bolt
11. Pull alternator out, a bit of wiggle and it comes right out
12. Put new alternator in,
13. Put bolts back in. The top one goes through the main pulley and ther is a little notch to make sure you orient it right. you should not over tighten, use a torque wrench if your not sure. If you want, you can replace the main pulley here, mine was fine. Remember to put the dust cap back on the main pulley.
14. Connect plug and main red power cable
15. Place main upper serpentine belt on while holding tensioner. It helps to have two people do this since your under the car and three hands help hold the tensioner and loop the belt on. Don’t force anything, the Germans made this logical and easy.
16. Put on the lower belt with tensioner loaded
17. Replace air filter housing and plug back in
18. Start and make sure everything works. I cleared the error code low cost OBD reader I bought on line years ago, works fine.
19. Replace bottom shroud and your done!

The old alternator was bad at 45,000 miles. Looks like a spun bearing or something loose inside it. It never froze, but it produced no power and sounded terrible. The replacement BOSCH unit was a perfect match and works fine. You can buy a completely new OEM unit for 4 times the cost, there no guarantee it will last longer.

Happy wrenching.
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      09-29-2014, 07:44 PM   #2
papitosabe
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what was the sound like that it made. Like a coffee grinding, scratchy kind of sound?
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      09-30-2014, 10:23 AM   #3
JimG Z4
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Quote:
Originally Posted by papitosabe View Post
what was the sound like that it made. Like a coffee grinding, scratchy kind of sound?
I'm wondering the same thing. Mine only acts up when it's idling - give it some gas and the sound goes away. It sounds more like a rattle than a grind. And it is coming from the alternator. My car only has 37k miles. Do these things fail that quickly?
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      10-09-2014, 05:05 PM   #4
Frank851
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Guys:
You could have just replaced the voltage regulator on the alternator. The grinding / crunching sound is probably from the contacts on the voltage regulator. The replacement regulator comes with the new spring loaded contacts in place.

Look at this post for part numbers and photos of what I used.

http://www.zpost.com/forums/showthre...or+replacement
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      10-20-2014, 04:35 PM   #5
fastgaas
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Probably could have just replaced the regulator if I had known. The noise was hard to pin down, sort of a loose bearing sound with rattle.
However, the unit then went into full failure, whatever was loose broke free and trashed the inside of the Alt. At $170 bucks I replaced the whole unit. The regulator only would not have saved me much and I felt better with a complete new unit.
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      10-22-2014, 06:50 PM   #6
ZStig
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I have an extra alternator for sale if anyone needs
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      10-22-2014, 09:48 PM   #7
papitosabe
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the grinding or rattling type of sound is usually the the bearing inside the alternator. The front bearing. An alternator repair shop can swap out the bearing for like $30 in an hour. At least that's what they charge in Houston. Plus the price of the bearing. They're about $10 for a German made bearing by F.A.G.

If you check the alternator voltage and its a voltage issue, its either the voltage regulator, which many times its just the brushes inside the regulator which you yourself if you can solder. Brush kits are $10-$15 http://www.ebay.com/itm/BOSCH-11523-...5867a2&vxp=mtr Or as someone stated, you can buy the entire voltage regulator.
Here is a DIY www.youtube.com/watch?v=bTcMD5_EznI



It can be the slipring http://www.ebay.com/itm/Bosch-Altern...e54d52&vxp=mtr which is a pain in the as to replace. Also around $15, but not sure labor cost, and I wouldn't recommend DIYing that. This is usually if its VERY worn. Sometimes all it take is some fine grit sandpaper, and lightly sanding it you can do yourself with no need for replacement.

************

"Too low charging voltage during the testing process can be caused by several factors, e.g., the following alternator parts might be defective: regulator, slip ring, carbons(brushes), diodes, winding.
If, however, the alternator makes noises during operation, this will point to defective bearings or a defective clutch pulley."

http://www.alternator-parts.com/

Last edited by papitosabe; 10-22-2014 at 11:01 PM..
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