Ballast ignition

We often find cars with an odd combination of ignition parts. This can lead to all sorts of problems.

Originally, the ballast system was fitted to cars between 1984 and 1990 (and to 1992 with 998cc Minis).

Here's how a Mini ballast ignition works....

  • It runs a 9v coil.
  • There will be two wires to the positive side of the coil.
  • The white/yellow wire is a normal wire supplying 12v.
  • The white/pink wire is a 'resistor' wire. This has 12v in, but a resisted 9v out to the coil.
  • When the ignition switch is in the 'engine running' position, the resistor wire is connected to the coil feeding the required 9v. The 12v wire is disconnected.
  • When you crank the engine on the starter motor, it also connects the 12v feed to the coil. This over charges the coil to help starting. Once the engine starts and the key is released, the 12v feed is once again disconnected leaving just the 9v feed.

As an aside, if you retrofit an electronic ignition, they generally need a 12v supply. You cannot take this supply from the coil on a ballast system since it is only running 9v. You should take a switch feed from the fuse box (plain white wires).