HOW TO REPLACE THAT LUCAS GENERATOR

WITH A DELCO ALTERNATOR

By George Kinai

     Yes, you read it correctly. But your Healey is positive ground? No problem. Read on. 

     Why would you want to replace the generator and its regulator? If you need to replace either one, cost is one factor. You can get a rebuilt Delco and a new regulator for as little as $30. In fact, you can probably get a used alternator for $5 to $15. Plus, the alternator has weight and efficiency advantages (keeps the battery better charged).

     The alternator can be modified for positive ground. You should get yourself an early model, external regu1ator, 35 amp Delco alternator (like for a ’63 – ‘ 68 Chevrolet). The following conversion can be made by your local rebuilding shop; or, it isn’t all that difficult to do at home.

     Modification Procedure - The Delco unit has 6 diodes, 3 of each polarity. The idea is to swap these triplets. If you want the utmost reliability, or are starting with a unit with burned out diodes, you may want to buy a set of new diodes.

  1.  Unscrew the 4 long bolts which hold the case together.

  2.  Carefully and s1ow1y separate the halves. Unscrew the three nuts which attach the outer (armature) winding leads to the diode connection points. Label or arrange the leads so they will be properly reconnected.

  3.  Remove brush holder.

  4.  Unscrew terminal nuts and condenser lead, enabling the 3-positive diode holder to be removed. Note arrangement of insulating washers as you disassemble

  5.  Press out all 6 diodes, noting which are the 3 positive diodes, and which are the 3 negative diodes (in the case itself). To press out diodes, use a sma1l (3/16 or so) socket to press the diode, and a 5/8 " socket to absorb pressure on the holder or case:

This can be done in a vise for the holder, but a large C - clamp or press is needed for the diodes in the case. The diodes can also be hammered out, but this is somewhat risky.

  1. Press diodes in - put the positive ones into the case, the negative ones into the holder. A 1/2" socket works nicely to press then in.
  2.  Reconnect and rewire diode leads, condenser, etc. Be sure to reassemble with proper arrangement of insu1ating washers.

  1. There is one trick in replacing the shaft and reassembling the case halves. The brushes must be held back in the holder. Notice there is a small slot below the holder. Take a piece of thin iron or copper wire and push it through this slot, across the face of the brushes pushing them into the holder, and then out the case through the venti1ation slot. Tighten the wire up. Assemble the case. Cut the wire and extract it, releasing the brushes.

     There are three testing procedures which you can use as you go along. First, after all diodes have been pressed in, they shou1d be checked with an ohm-meter in both directions. Current should flow in only one direction in each diode. When the alternator has been assembled, an ohm-meter or a small bulb and battery (see Figure) should indicate that current will flow in only one direction between the output ("BAT") lead and the case. It is also possible to bench test the alternator with an electric motor, but remember that a battery is needed to provide initial excitation and to limit peak output voltage to protect the diodes. Anyway, the idea is to be reasonably sure you have a woking unit before installing it in the car.

TEST FIGUIRE

 

 

MECHANICAL INSTALLATION

     You;re on your own here. Go to a junkyard and find alternator brackets which look like they’ll work. Attach by bolts or welding to the generator bracket. The tensioning adjustment bracket can be made up by combining two of the curved brackets common on alternator equipped cars of many makes. You will probably need to use a belt of different length than originally, depending upon the exact installation.

WIRING (color code per MKIII wiring)

At the alternator:

     (sane as in        Brown - Y to output (fat stud)

     generator)         Brown - Gr              Field (F)

                             New wire to "R’ terminal

At the Regulator (new):

Thin Brown - Y (from idiot light) - to terminal   underneath reguIator

Fat Br - Y (from alt. output) - term. #4

New wire (from "R") - term. #2

Brown wires (4) splice together, connect to term. #3

Brown - G (from alt. F) - terminal "F"

Editor’s Note: Interested in such converted polarity alternators? Contact George at 636 So. Carolina Ave. SE, Washingtou, DC 20003.