The 'E' Type Forum

hello everybody, i'm bothering you because my jag has a dynamo to alternator replacement for over 30 years now, and the alternator is converted to charge on ground +. The thing is that i bought a Pertronix points replacement with a flame thrower coil, but when i replace the poins and connect everything like the instructions, A: The war wont start, B: The alternator doesn´t charge.

It's like if I replace the points as its connected, ther's a electrical mess and the coil doen't send spark, or, if i miss the ignition cable the car starts, but the alternator doenst charge. Is driving me crazy.

So if anyone made the pertronix convertion maybe could explain me how the wires diagram work.

Hi Carlos

If you changed from a dynamo to alternator I would have thought the car would also have been converted to -ve earth. If your car is still +ve earth then the Petronix will not work unless you specified the positive earth version. Can you confirm yours is +ve ground (earth) - it should say on the instructions. If you used the wrong one you may have blown the diodes in the alternator.

Easiest thing to do is put back the original contact breaker and see if the car runs and charges.

More helpful info here: https://mgaguru.com/mgtech/ignition/ig205.htm

"Apparently the Ignitor modules for positive or negative earth are the same except for the color of one wire. Being designed for negative earth connection, the positive earth installation must rearrange the wire connections to keep current flowing the same direction through the electronic module. When you order one for positive earth application it comes with one wire in a different color and different instruction paper for installation."

yeah, i bought the + ground version, and the one who made the transformation from dynamo to alternato made the alternator charge on (-) so the car could still run with (+) ground. I think theres a wire conected rarelly, i have a external mechanic volt regulator, so its a little easyer, but still.