the c40 dynamo and its pulley

[oldelanman]

I'm sure that I read somewhere that the RB340 was fitted to the elan only as negative earth.

Workshop Manual (section M Page 45)

[dgym]

It is refreshing to have a car like this, where originality is different across all cars. It kind of gives you a reminder every now and then that you should be enjoying the thing rather than spending hours on the internet searching for magical parts. Well done Lotus

there appears to be only a difference of two connections in the schematic between the rb106 and rb340, involving the ignition warning light having it's own connector.

so, if the screws line up with the rb340, I do believe my car already had it, perhaps i will slightly alter my schematic instead of drilling holes in the body for the rb106.

also found this in the manual, discussing polarity. (probably should have looked through this long ago..d'oh. )

[dgym]

Ok I'm back and hoping to get some support for the job at hand.

I've acquired the pulley and brackets for my dynamo and I have the control box so I think I'm ready to bite the bullet and make the switch back to positive earth.

So here's my list.
1. disconnect battery
2. remove tacho and convert back to positive earth, re install.
3. remove alternator, install generator and wiring.
4. install control box and connect wiring as per schematic.
5. swap leads on coil??..
6. re connect battery with positive to earth
7. polarize generator

other than that I am a little confused about the relays, would I need to swap positive and negative here?

cheers!

[Galwaylotus]

Yes. Swap the coil connections.
No. Relays are not "directional".

[rgh0]

deleted post

[dgym]

Ok thanks gents,

I just put the multimeter on the coil from the -ve to the outer case and didn't get a connection so I think I'm ok there.
..If I understood you correctly Rohan?

[oldchieft]

Sorry, it I have not followed the post correctly, but I believe the primary winding should have a taping on to the secondary.

This is so as the magnetic field collapses a voltage is induced in both windings and the taping adds the induced current together to give a fatter spark. This page is a general guide to what a coil should read.

http://www.secondchancegarage.com/publi ... ooting.cfm

Hope my memory is correct on this.

Jon the Chief

[Galwaylotus]

On the coils I have, earth is earth for both primary and secondary windings. In any event, for non-directional items such as switches (including relays), bulbs and starter I believe we need to think more "supply" and "earth" instead of positive and negative. The tach is directional and the reason for changing the coil polarity is so that the spark jumps the gap in the plug in the optimum direction. As far as the voltage supplied by the coil, it doesn't matter which way it's connected.

[oldchieft]

As far as the voltage supplied by the coil, it doesn't matter which way it's connected.

Don't think that is quite true, the induced voltage in the primary when magnetic field collapses should be with the induced voltage in the secondary windings not opposing it. I seem to remember when I was at tech school this was demonstrated on the oscilloscope of the Sun tuner in the workshop.

http://cny.mgcarclub.com/electrical_systems.htm

There is a bit of detail in the drawing on this site.

Jon the Chief

[Galwaylotus]

My point was that as long as everything in the coil circuit is reversed it shouldn't matter in which direction the current is flowing. Perhaps I'm missing something?!

[AHM]

Coils have 2 terminals and neither are earth.

Old coils are marked SW (ignition switched 12v supply) and CB ( Contact Breaker - switched ground)
Newer coils are marked + and - which is fairly self explanatory

As far as I am aware SW and CB markings relate to positive earth and on the introduction of negative earth were replaced by + and - for universal use.

The body of the coil should be earthed for some very technical reason, but is not electrically connected to either coil ( at least not on any of the coils I have ever come across)

[Galwaylotus]

Coils have 2 terminals and neither are earth.

Old coils are marked SW (ignition switched 12v supply) and CB ( Contact Breaker - switched ground)
Newer coils are marked + and - which is fairly self explanatory

As far as I am aware SW and CB markings relate to positive earth and on the introduction of negative earth were replaced by + and - for universal use.

The body of the coil should be earthed for some very technical reason, but is not electrically connected to either coil ( at least not on any of the coils I have ever come across)

That's correct. Neither is earth; however, one side is connected to earth via the distributor to spark plug to engine to battery path. It doesn't matter whether this earth is +12Vdc or -12Vdc. It's still the system earth.

[billwill]

Coils have 2 terminals and neither are earth.

Old coils are marked SW (ignition switched 12v supply) and CB ( Contact Breaker - switched ground)
Newer coils are marked + and - which is fairly self explanatory

As far as I am aware SW and CB markings relate to positive earth and on the introduction of negative earth were replaced by + and - for universal use.

The body of the coil should be earthed for some very technical reason, but is not electrically connected to either coil ( at least not on any of the coils I have ever come across)

That's correct. Neither is earth; however, one side is connected to earth via the distributor to spark plug to engine to battery path. It doesn't matter whether this earth is +12Vdc or -12Vdc. It's still the system earth.

This seems ODD, since the spark is generated when the points open not close, the coil isn't actually connected to earth at that time.

[dgym]

well i'm a bit lost.

I also found this which I'm trying to understand :
http://www.britishcarspecialists.com/pd ... basics.pdf

I was slightly disappointed to see that the coil in my car has the + and - markings rather than SW and CB.

[Galwaylotus]

This seems ODD, since the spark is generated when the points open not close, the coil isn't actually connected to earth at that time.

If it wasn't there would be no spark!! The HT side of the coil puts out some 15k volts but voltage is a potential and to spark it has to find its way to earth. In this case that's via the distributor and spark plug. The points break the primary circuit (low voltage) allowing the secondary side (high voltage) to come into effect when the field collapses generating a voltage.