Nearly there! I rigged the system up as in your diagram except I haven't got the 'S' terminal so just used the IG and L.
Charged the battery all night so that I am getting 12.7v at the coil with nothing connected to the alternator. Rigged it up as shown and the bulb lit up
However, I then checked the voltage at the coil and it was reading 12.01v. After a few more 'experiments' I was noticing that as soon as I put the live ignition feed to the alternator, thats what seemed to be affecting the voltage drop, this is even without the bulb connected. In fact what I did was watch the voltage as I connected the lead and it drops to about 12.3 then fluctuates with readings down to 11.98v for a few seconds and then stabilises at 12.01v.
The coil will draw 5 to 8 amps wit the ignition on, which enough to drop the reading below 12v.
The starter will cause more of a drop, but if all is setup correctly, the motor should start.
If not, the problem will be one of:- (Not enough) Spark; Fuel or volts to spin the starter.
S
********************************************************************************
* Swinging the World by the tail since 1960 *
********************************************************************************
The regulator should sense the battery voltage through the IG terminal.
S
********************************************************************************
* Swinging the World by the tail since 1960 *
********************************************************************************