Thread: PIcs of a Tdi alternator rebuild

After my alternator's bearings died, I decided to pull the old one apart and see what makes it tick. It turned out ot be relativly simple so I rebuilt it - here are some pics and tips:




This is what you start with. Those little nuts above the +ve post hold the regulator down. You'll need a 5mm,5.5mm 6mm and a 7mm socket to get it off. Take the plastic cover off the back and those wire stubbs you can see around the edge of the cover need to be de-soldered from housing. A small butane soldering iron won't be able to handle it - use a big mutha (And plumbing quality solder- has a higher melting point).





This is what happens if you hit it with a hammer.

After you take the front pulley off, and undothe casing, refit the pulley nut onto the shaft to protect the front thread and tap gently That will split the case and the front half should come off easy. Use a wood block to protect the rear shaft when removing it from the rear half of the case.

You are going to need a small 2 post gear puller (Less than 3 inch). Or press with appropiate fittings. The rear bearing will most probably be frozen on, and also be r**ted.



This is the rotor from a dead rangie alt I had leftover, same design and the slip rings weren't too bad. You can actually replace the rings, they disconnect from the rotor windings easy if you want to - finding the part will be difficult


Undo the bearing holder in the front half, and tap out.



Now this is the good part: Go to CBC and get a rubber seal 6303 and 6003 bearing. Pay $9 ea (inc GST). I use emery paper to smooth the bearing holder and rear shaft so the bearings slide on. Makes life easier, some may disagree. This is the time I also smoothed the slip rings on the rotor



Bolt back together. The half circle item is the rectifier with diodes. It's a one piece unit, looks like the diodes are not replaceable. The rectifier is split in half on the bottom (Behind shaft). The left side has a silicone insulator you can just pick out, and the right half is uninsulated. I used normal heat conductive paste (Dick Smiths, $3) and cleaned all the junk off the base and terminals.Remember to clean off excess paste, as it's conducts electricity The bottom slip ring cleaned up OK, but the top still has a bit of a groove in it.




This is the regulator, MM type 24TR, PN 28018A. As usual, none of the auto electricians I visited had any idea about this part. All the terminals needed cleaning with steel wool, and the brushes undo and slide out from the box section at the bottom of the regulator. Brushes are at top right of pic. Be gentle with them, and square them off with a small file.

Put it back on, resolder the wires to the rectifer, refit pulley and back plate and that's it.

At least you know whats inside if yours dies.

Langy

Originally posted by Bushie
More info on the Megneti Marelli unit here

http://members.ozemail.com.au/~defender110...tor_service.htm


Bushie

Excellent, that's the Defender MM alternator, thanks Bushie. 8)
I'd saved those pages years ago, but when I tried the link I had to post on here, it wouldn't work.