Technical Information (MGB 6)

Alternator Conversion Kit - MGB 1963-1967

Last Modified - 3/8/01

This alternator conversion requires the electrical system to be converted to "NEGATIVE GROUND".

The appropriate USA engine block ID numbers for these years are as follows:

18G and 18GA (3 main bearing) and 18GB (5 main bearing). These engine blocks had no provisions for alternator mounting purposes. Beginning in 1968, generators were discontinued in favor of Lucas alternators. These later engine blocks, 18GK, thru 18V had provisions for mounting both alternators and generators. Due to engine interchangeability you may or may not require alternator mounting bracket Part 12G1053.

In 1968 alternator Part 23548 (34amp) became a standard fitment with an external voltage regulator. In 1969 Part 23716 (34amp) was introduced incorporating an internal voltage regulator with a 5 terminal type connector. In 1972-73 saw the introduction of a newer style alternator Part 23804 & 23748 (both 34 amp) with a simplified 3 terminal connector plug Part 54960402, this continued thru mid- 1974. At this time yet another style of alternator was introduced Part 23756 (A1816 43 amp) with a different connector plug assembly. This alternator fitment continued into 1978 thru ID number 471000. From ID number 471001, yet another alternator was introduced Part 23737 (A1812 43 amp) using Part 54960402 style connector plug.

We find alternators A1611 or A1812 to be more convenient for this conversion. You will need a heavy duty-soldering gun to accomplish the following installation.

INSTALLATION INSTRUCTIONS FOR ALTERNATOR CONVERSION KIT (A1816 & A1812) MGB 1963 THROUGH 1967

1. Disconnect battery ground terminal.
2. Disconnect tachometer hot supply wire.
3. From the regulator, remove both indicator warning light (small brown/yellow) and generator field wires (brown/green). Remove insulated ends and join together using Part NOB524H sleeve.
4. Remove generator output wire (large brown/yellow) from the regulator and attach to the battery side of the starter solenoid.
5. Remove generator assembly.
6. Install rear generator mounting bracket Part 12G1053.
7. Install A1611 alternator with original adjusting bracket or go to Step 11 if you are installing A1812.
8. Connect the original generator output wire to the center terminal on alternator and connect the original generator field wire to the small terminal. If you feel so inclined you can use connector kit Part 54960402 and solder the new terminals to the existing wires.
9. Install and adjust fan belt.
10. We normally leave the existing voltage regulator in place. If you decide to remove the regulator then you will have to join the brown wires together. You can also leave the black wire in position or discard. (SKIP TO NEXT SECTION)
11. Using connector kit Part 54960402 solder terminals to existing generator output and field wires.
12. Determine the length of 12AWG wire required running from the alternator to the battery side of the starter solenoid. Solder the remaining connector kit terminal to one end of the wire and, at the other end, solder an appropriate terminal eye.
13. Plug the 3 alternator terminals into the connector base and snap on the cover. Attach terminal eye to battery side of starter solenoid.
14. As in instruction 9 above.
15. As in instruction 10 above.

DO NOT HOOK UP YOUR TACHOMETER UNTIL YOU HAVE THE UNIT CONVERTED TO NEGATIVE GROUND.

At this time you may consider converting your 6-volt batteries to a single 12-volt unit. You will find that Interstate Battery Systems Part MT26 is conveniently sized. Use Part BHCB Bracket BHB10J Bolt Kit and B9 Battery ground cable to complement the installation. Remove the original 6-volt battery interconnecting cable

If your battery box is corroded install a plastic battery holder. Part is available from various vendors. In this case you will not require the BHCB or the BHB10J. Be sure to lay some kind of insulation on top of the battery terminals to prevent contact with the battery box cover.

NOTE:Some A1611 alternators required an additional wire (brown) to excite the internal regulator. If your alternator does not charge it could be due to this missing wire. Therefore, simply run an additional 14AWG wire from the outer alternator terminal to battery side of the starter solenoid.

Batteries are normally sold in group sizes with various small differences in dimensions. We have found the Interstate MT26 to be the ideal size.

Components supplied by British Automotive are as follows:

Components to be sourced by the customer are as follows:

For tachometer positive to negative ground conversion see Moss Motors MGB parts catalog. For rebuild services check with Nisonger Instrument Services (914) 381 1952 EST.