Ballast Resistor

[Wangler]

I'm upgrading to a 123 ignition and a Bosch Red coil so I need to remove any ballast resistor in order to use this coil.

I'm pretty sure my S3 has a ballast resistor as the voltage with the ignition turned on is 10.5v whilst the voltage at the battery is 12.3.
The resistance of the primary coil (looks like the original Magneti Marelli) is 2.7 Ohms.

Please could someone tell me where the ballast resistor is located?

[lancialulu]

Normally as part of the coil assembly. Your coil resistance indicates you should not have a ballast resistor to my mind. low voltage at the coil could possibly be due to the ignition switch being dirty or poor fuse box.

[nistri]

Furthermore, 12.3 V at the battery is quite low and it is likely the battery will soon stop working efficiently. The ballast resistor is a small box sitting on top of the coil to which it is connected, Andrea

[Wangler]

Thank you both.

There's no sign of a small box sitting on or near the coil. I've also looked at the wiring diagram for 2nd Series and can't find any sign of a ballast resistor, so I guess I don't have one.

The apparent voltage drop is surprising to me, but the car is 47 years old and although the electrics seem quite good they are virtually all original. I'll measure the voltage at some other locations and see how they compare.