Diode Trio Replacement
Race Director
Joined: Dec 1999
Posts: 16,945
Likes: 9
Mark the housing halves before taking them apart or you'll be clocking them later on for the proper orientation
When you're in there replace the bearings
Check the contact ring for excessive wear
When putting back together, keep the brushes in place with pieces of steel wire, there are little holes in the brush guides and the back housing for this purpose
When you're in there replace the bearings
Check the contact ring for excessive wear
When putting back together, keep the brushes in place with pieces of steel wire, there are little holes in the brush guides and the back housing for this purpose
Racer
Joined: Dec 2005
Posts: 325
Likes: 0
From: Partlow VA
It's really pretty easy except for the brushes. Mark the two half’s so they go back in the same position, check the other components while you have it apart! When everything looks good just install the brushes back in there holder and use a straightened out paper clip to retain the brushes during the reassemble, you’ll see a hole in the brush holder were the paper clip will fit. 
Advanced
Joined: Nov 2006
Posts: 61
Likes: 0
From: The one I'm in at the time. High country Colorado,Maui.
Try Auto Zone or Napa.
But why do you think the pack is out? Most of the time the regulator or brushes will fail first. Also it is not that much for a reman alternator. Is there a reason you do not just replace it?
But why do you think the pack is out? Most of the time the regulator or brushes will fail first. Also it is not that much for a reman alternator. Is there a reason you do not just replace it?
Melting Slicks
Joined: Feb 2006
Posts: 3,105
Likes: 96
From: Sunrise FL
You can ohm out the diodes with a multimeter set to diode check. Must be done with the trio not connected to the field coil, and ONE diode at a time. Lift the tabs a little.
Hi resistance one way, reverse the leads and read 500-1000 ohms.
Hi resistance one way, reverse the leads and read 500-1000 ohms.
Thread Starter
Pro
Joined: Dec 2004
Posts: 534
Likes: 2
From: Connecticut
Originally Posted by If you can
Try Auto Zone or Napa.
But why do you think the pack is out? Most of the time the regulator or brushes will fail first. Also it is not that much for a reman alternator. Is there a reason you do not just replace it?
But why do you think the pack is out? Most of the time the regulator or brushes will fail first. Also it is not that much for a reman alternator. Is there a reason you do not just replace it?
Team Owner
Joined: Jul 1999
Posts: 65,492
Likes: 230
From: Orange Park Florida
OK, guys, first off, all GM alts are Delta wound...so therefore the outputs supplying the actual power are passing through 6 diodes, not just 3, and the field is floating at a nominal 6-7 volts.....the trio everyone referrs to is off the positive side of the delta....running parallel with the main power ones, and feeds the regulator...I dunno why it is that way, just is/was....
the main diode stack is in a fairly large heat sink, and the early alts had diodes we can actually see, if familiar with electronics....
starting early '70's all that changed, and the diodes were no longer that apparent, to a geek...they are, but not the typical homeowner/mechanic....
the main diode stack is in a fairly large heat sink, and the early alts had diodes we can actually see, if familiar with electronics....
starting early '70's all that changed, and the diodes were no longer that apparent, to a geek...they are, but not the typical homeowner/mechanic....
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Burning Brakes
Joined: Aug 2005
Posts: 1,126
Likes: 0
From: Hudson Falls, N.Y. 76 Vette Modified L-48
Originally Posted by Vettkeeper
It's really pretty easy except for the brushes. Mark the two half’s so they go back in the same position, check the other components while you have it apart! When everything looks good just install the brushes back in there holder and use a straightened out paper clip to retain the brushes during the reassemble, you’ll see a hole in the brush holder were the paper clip will fit.
Race Director
Joined: Sep 2001
Posts: 10,560
Likes: 439
From: Wellington, FL
St. Jude Donor '11 thru '25
My suggestion would be to buy a reman from one of the major parts houses. At Advance they're around $40 and come with a lifetime warranty. If you have original alt., take it apart and swap the half that has the casting numbers with that of the reman. Then use this old alt as your core. You then end up with a completely remanufactured alt. with a lifetime warranty which reflects the correct casting numbers. I would not mess around spending as much or more in parts and rebuilding your old one yourself. As a side note, you may want to paint your new one with alt. type paint so that that both pieces match. Just my 2 cents.
Last edited by Jud Chapin; Nov 23, 2006 at 07:24 AM.
