W126 upgraded alternator! AL129X - PeachParts Mercedes-Benz Forum

LandYaghtLover · #1 04-21-2011, 01:21 AM

Well a couple weeks ago I replaced my voltage regulator on the back of the alternator. It had improved consistent voltage output. Or so I thought. Yesterday the car had a difficult turnover incident. And when fired up, the rear defrost switch was flashing! Voltage had to be low. It drove fine the rest of the day though for the most part with things either working or running low voltage. Very intermit ant.

Anyway, after some voltage readings something was not right. So I ordered the AL129X Audi (or Saab?) alternator everyone seems to recommend. The 110 amp upgrade is certainly needed over the stock 60 amp anyway and it was something I was planning for this summer.

The unit is not the same. I did re-use the original pulley, fan, spacers, etc. So no belt alignment issues. Besides, the new one had non of that. But the electrodes are on the opposite location. On the old they are towards the top. With the new, at bottom. That is a problem with my 91. When swung down the electrode comes into contact with something coming off of the block. I am not sure what the setup is, but its a valve that touches. I had to really crank down on the belt to prevent contact. The stock cables were no issue though, plenty of length. But I can not swing the alt all the way down. I will always have to install longer than stock sized belts.

Things seem fine now. I cleaned all the metal on metal contact points and bolts. I also installed a second ground strap from alternator to body frame.

With the old alt at idle it read 13.XX and would NOT increase under increased RPM. Back when I installed the new reg, I was getting about 14.5. So something had degraded since then. And voltage should go up with increased engine speed. With the new I get about 14.1 at idle. With everything turned on it drops, but with increased engine speed voltage quickly recovers as it should.

Not a hard job to do. Now I have a very slightly used Bosch regulator if anyone is interested. From what I read it will not be of any use on a 110 amp alternator.

Rick76 · #2 04-22-2011, 06:26 AM

You can undo the 4 long bolts that hold the two halves of the alternator together and rotate the back so the terminals are in a better position.

LandYaghtLover · #3 04-22-2011, 11:57 AM

Yup, found that out from the parts guy. Said they usually can be swapped.

Hit Man X · #4 04-24-2011, 02:15 AM

Quote:

Originally Posted by Rick76

You can undo the 4 long bolts that hold the two halves of the alternator together and rotate the back so the terminals are in a better position.

This is what I did too.

LandYaghtLover · #5 04-26-2011, 12:13 PM

Rotation worked. If anyone tries, remove long screws but do not try to separate. At first I did, but it simply twists. You will also probably want a light impact drill to get them started. Mine were on pretty tight. Thread lock is something I recommend.

Hit Man X · #6 04-26-2011, 10:01 PM

On with the pics!

LandYaghtLover · #7 05-02-2011, 12:19 PM

Pics? Its an alternator. The only was was dull, the new is pretty!

I actually had to swap it out again for another. The first was noisy.

Anyone know the difference in BOSCH regulators? I am using the one provided with the unit, but I have one hand for the 60 amp alt. Would it work on the 110 amp alt? Each one I have, from my first faulty to the newest on the 110, has a different part number.

Abdullah · #8 05-03-2011, 12:18 PM

Quote:

Originally Posted by LandYaghtLover

Well a couple weeks ago I replaced my voltage regulator on the back of the alternator. It had improved consistent voltage output. Or so I thought. Yesterday the car had a difficult turnover incident. And when fired up, the rear defrost switch was flashing! Voltage had to be low. It drove fine the rest of the day though for the most part with things either working or running low voltage. Very intermit ant.

Anyway, after some voltage readings something was not right. So I ordered the AL129X Audi (or Saab?) alternator everyone seems to recommend. The 110 amp upgrade is certainly needed over the stock 60 amp anyway and it was something I was planning for this summer.

The unit is not the same. I did re-use the original pulley, fan, spacers, etc. So no belt alignment issues. Besides, the new one had non of that. But the electrodes are on the opposite location. On the old they are towards the top. With the new, at bottom. That is a problem with my 91. When swung down the electrode comes into contact with something coming off of the block. I am not sure what the setup is, but its a valve that touches. I had to really crank down on the belt to prevent contact. The stock cables were no issue though, plenty of length. But I can not swing the alt all the way down. I will always have to install longer than stock sized belts.

Things seem fine now. I cleaned all the metal on metal contact points and bolts. I also installed a second ground strap from alternator to body frame.

With the old alt at idle it read 13.XX and would NOT increase under increased RPM. Back when I installed the new reg, I was getting about 14.5. So something had degraded since then. And voltage should go up with increased engine speed. With the new I get about 14.1 at idle. With everything turned on it drops, but with increased engine speed voltage quickly recovers as it should.

Not a hard job to do. Now I have a very slightly used Bosch regulator if anyone is interested. From what I read it will not be of any use on a 110 amp alternator.

Here what I have already done to my Alternator upgrading, it is working perfectly, I noticed the electric cooling fans working efficiently, even in the stop/and go traffic, they work aggressively, also AC fan became noticeably different and much better. I think it is good for those who put DVD and/or CD players and need extra power. This modification may be useful for someone in the future.

http://www.4shared.com/video/D61ImdPX/Upgraded_Akternator1.html

http://www.4shared.com/video/7_oVbe8-/Upgraded_Alternator2.html

tjts1 · #9 05-03-2011, 12:29 PM

Quote:

Originally Posted by LandYaghtLover

Anyone know the difference in BOSCH regulators? I am using the one provided with the unit, but I have one hand for the 60 amp alt. Would it work on the 110 amp alt? Each one I have, from my first faulty to the newest on the 110, has a different part number.

I think the cut off point is at 90a before you need a different PN.

I replaced the worn down Bosch 14.0v regulator with a Huco(?) 14.5v on my stock 70a alternator. Now I have 13.8v at idle no matter where I measure it in the car with accessories turned on. It was a cheap fix for me. The brushes on the old regulator were very worn down. I was lucky to see high 12s with all the electrics running.