12v conversion and Lucas ignition and light switches
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LynP
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- Location: GWENT UK
12v conversion and Lucas ignition and light switches
I am converting my 1961 G12 alternator model to 12v using combined regulator/rectifier. Please can anyone tell me if I need to remove or insulate any wiring from the Lucas ignition or lighting switches or can I just leave the switches wiring as it is? The switches are original. Thanks for any guidance. Lyn
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Groily
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Re: 12v conversion and Lucas ignition and light switches
This is a short question, but not a short answer! (And please note, what follows applies to typical Single Phase Alternators - three phase ones need slightly different treatment and a different regulator/rectifier.)
The great advantage of using for example an A Reg 1 or other 12v regulator/rectifier is that the wiring can be simplified considerably. Indeed, can be reduced to about a dozen wires in total, cutting down on possible points of failure, the number of snap connectors, etc etc.
On your original wiring there will have been 2 wires from the alternator that went straight to the old rectifier, and one that went straight to the ignition switch to provide Emergency Ignition so-called.
The rectifier will have had a wire going to each switch and thence, via the ammeter, to the battery.
The switches controlled not only what was 'on' but also the rate of output of the alternator - by switching fewer or more of the three pairs of coils into circuit depending on the needs of the system. Effective enough, but fairly primitive.
A typical two switch (lights and sparks) coil ignition system looked like the diagrams on page 71 and page 72 of the attached pdf, for RM 13 and RM 14 alternators as fitted to singles and twins respectively. Variations on the theme are numerous, but the basics don't alter much. Page 71 provides a typical full schematic, page 72 a more limited one. Both show some of the numbering found on standard switches of the era. A meter will show how whatever switches you have get juice from one terminal to another.
When you fit a combined regulator / rectifier, though, you do away with the need to manage the alternator output according to the demands on the system, because the new box of tricks controls the output all on its own.
Older 3 wire alternators need a pair of wires doubled up (see Paul Goff's website for more on that) and later 2 wire ones are simply connected one wire to each of the AC terminals of the new regulator/rectifier. Doesn't matter which way round. A permanent magnet alternator is 'working' full time, all the time, and potentially excess output is now dispensed with at the regulator, not by switching alternator coils in and out off action.
All that is needed is to connect the live side DC output from the reg/rect - it's your choice which side to earth - to the ammeter and then to the 'power in' terminals of both switches. (Or to one switch then the next and then the ammeter - it makes no odds).
The other side of the ammeter will be connected to the battery (via a fuse for choice). So any power drawn by either switch will show up on the ammeter, which will also register the charge going to the battery.
Your lighting switch will remain as it was for power to the dipswitch, and for the tail and speedo lights, and for the separate front sidelight if you want it to go out with the headlight on (or if you want it all, for what little it's worth). Your ignition switch now has to feed only the coil using power drawn from the battery via the ammeter, operating as an on/off switch basically.
The upshot is that a fair bit of any standard harness becomes redundant.
Obviously one could use a standard set-up and just disable the things that aren't required, or simply make something more straightforward.
The key elements are:
*Alternator wires to new reg/rect - 2 wires, or 1 separate and a spliced pair (on older versions);
*earth from reg/rect;
*live DC wire from reg/rect to ammeter and both switches in whatever 'order';
*live feed to coil from ign switch;
*and the previous wiring for the lights.
*Plus horn and brakelight, probably straight off the battery.
A very basic schematic which doesn't show switch terminal numbers, and the Lucas circuit diagrams are attached . . . Hope it helps a bit.
The great advantage of using for example an A Reg 1 or other 12v regulator/rectifier is that the wiring can be simplified considerably. Indeed, can be reduced to about a dozen wires in total, cutting down on possible points of failure, the number of snap connectors, etc etc.
On your original wiring there will have been 2 wires from the alternator that went straight to the old rectifier, and one that went straight to the ignition switch to provide Emergency Ignition so-called.
The rectifier will have had a wire going to each switch and thence, via the ammeter, to the battery.
The switches controlled not only what was 'on' but also the rate of output of the alternator - by switching fewer or more of the three pairs of coils into circuit depending on the needs of the system. Effective enough, but fairly primitive.
A typical two switch (lights and sparks) coil ignition system looked like the diagrams on page 71 and page 72 of the attached pdf, for RM 13 and RM 14 alternators as fitted to singles and twins respectively. Variations on the theme are numerous, but the basics don't alter much. Page 71 provides a typical full schematic, page 72 a more limited one. Both show some of the numbering found on standard switches of the era. A meter will show how whatever switches you have get juice from one terminal to another.
When you fit a combined regulator / rectifier, though, you do away with the need to manage the alternator output according to the demands on the system, because the new box of tricks controls the output all on its own.
Older 3 wire alternators need a pair of wires doubled up (see Paul Goff's website for more on that) and later 2 wire ones are simply connected one wire to each of the AC terminals of the new regulator/rectifier. Doesn't matter which way round. A permanent magnet alternator is 'working' full time, all the time, and potentially excess output is now dispensed with at the regulator, not by switching alternator coils in and out off action.
All that is needed is to connect the live side DC output from the reg/rect - it's your choice which side to earth - to the ammeter and then to the 'power in' terminals of both switches. (Or to one switch then the next and then the ammeter - it makes no odds).
The other side of the ammeter will be connected to the battery (via a fuse for choice). So any power drawn by either switch will show up on the ammeter, which will also register the charge going to the battery.
Your lighting switch will remain as it was for power to the dipswitch, and for the tail and speedo lights, and for the separate front sidelight if you want it to go out with the headlight on (or if you want it all, for what little it's worth). Your ignition switch now has to feed only the coil using power drawn from the battery via the ammeter, operating as an on/off switch basically.
The upshot is that a fair bit of any standard harness becomes redundant.
Obviously one could use a standard set-up and just disable the things that aren't required, or simply make something more straightforward.
The key elements are:
*Alternator wires to new reg/rect - 2 wires, or 1 separate and a spliced pair (on older versions);
*earth from reg/rect;
*live DC wire from reg/rect to ammeter and both switches in whatever 'order';
*live feed to coil from ign switch;
*and the previous wiring for the lights.
*Plus horn and brakelight, probably straight off the battery.
A very basic schematic which doesn't show switch terminal numbers, and the Lucas circuit diagrams are attached . . . Hope it helps a bit.
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LynP
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- Joined: Mon Jan 01, 1990 12:00 am
- Location: GWENT UK
Re: 12v conversion and Lucas ignition and light switches
Thank you Groily for taking the time and trouble to give such a detailed and useful answer to my question. The first Lucas diagram is really informative, especially with regard to the switch positions. As the wiring harness is original and seems in good condition if I do the 12v conversion I will just leave the redundant wires in position. Best regards, Lyn