I need to replace the voltage regulator - brush assembly on my Magneti Marelli 100 amp alternator. The alternator part number appears to be AMR 4247. Since the bearings are fine I'd rather not replace the entire alternator.

I've not been able to find the voltage regulator for this unit. Does anyone have any ideas for a source?

Thanks in advance!

 

Just out of curiosity, I did a search on the MM 100 amp alternator and found this, I had no idea the retail price was that high.
LAND ROVER PARTS - ALTERNATOR - 100 AMP V-8 - MAGNETI MARELLI

Then I found this:
http://www.car-stuff.com/MagnetiMarelliAlternator.htm

 

Alternator voltage regulators are basically just a switch. If yours is mechanical you can clean the contacts. If it is electrical and you can get it open without tearing it up, you can test for and find the faulty component and swap it out. Allied elec.com will have your replacement component. As for replaceing the entire unit. Buy used or call Bosch.

 

Just out of curiosity how did you determine the regulator to be bad instead of it being the generator?

 

I haven't isolated it 100% to the regulator. I suspect the regulator as the alternator is mechanically sound and turns freely, but their is a fluctuating component at the alternator output (about +/- 4v at 3 or 4 Hz) and the battery appears to have been overcharged.

Thanks.

 

Thats because it is waterproof.

 

I put my original one baCK IN AFTER THE USED ONE DID NOT CORRECT MY DEAD TACH PROBLEM.

IT IS A MAGNETI MARELLI.

 

If you place your positive volt meter lead to the positive battery terminal and negative volt meter lead to the nagative battery terminal you will see somewhere around 12.? volts. If you do this same test with the RPM's at or above 1500 you should see voltage from 13 - 14. If it is still normal battery voltage then yes voltage regulator/alternator. If the voltage is too high and way over 14 then yes voltage regulator/alternator. Are you blowing alot of fuses?

 

I was just looking at the RAVE test section yesterday. It talks about reving to 3000 and seeing 14.5 volts.

Mine is 13.7 or so. The used one I bought had already been remanufactured, but the output on it was not stable, so I returned it for a refund and put my MM back on. I satill have a dead tach, but I guess it is either a open wire or a bad tach in the instrument cluster.

I presume the voltage regulator is internal to the alternator?

Anyone have any info on the internals of the MM alternator?

 

Land Rover alt rebuild.


‪ALTERNATOR REBUILD PART 1 FROM DIY-DVDS.COM‬‏ - YouTube