Ballast Resistor?

[Dan stag]

It may be a dumb question but what is a Ballast Resistor, where is it and what does it do? Thanks.

[V Mad]

Dan do a search for ballast resistor it has been covered many times. The ballast resistor allows a boost voltage to be applied to the coil when cranking the engine. This is useful because it compensates for the drop in battery voltage.

In the Mk2 car it is part of the wiring loom, but on a Mk1 it is a component that is usually mounted alongside the coil.

[Dan stag]

Thanks I guess it's not something to concern me with a MK2.

[Bob Heritage]

Thanks I guess it's not something to concern me with a MK2.

Although a Mk2 is in the loom, it still works the same way, so yes it does concern you.

[Westfaling]

Dan
If the ballast resistor isn't in the circuit you'll feed 12 volts direct to the coil, which is rated at 6 volts. It will get very hot quite quickly and cook itself. The coil only gets 12 volts during start- up by a feed direct from the starter circuit. I don't know the failure modes for ballast resistors but I doubt they fail to zero resistance so I would suspect if it failed you'd have poor or no ignition.
Nick

[Dan stag]

Thanks now I know. Often seen it advertised and mentioned, no idea what it was.