Landrover forward control resister ballast in I may be stupid, but...... Posted May 22 The coil may have been changed from 6v to 12v if the ballast resistor has been removed. The original clamp with its warning may have been loosened & a 12v coil slid in. A Lucas coil should have the part number & date code stamped on the base (flat bit), this will indicate if it is 6v or 12v coil. Maybe the ballast resistor failed & a 12v coil fitted as a temporary fix or maybe someone thought they knew better than the designers & having a 6v coil + ballast resistor was a silly complication? Wired with a 12v coil it will still run but the performance will not be so good at high revs because the extra inductance of a 12v coil over a 6v coil slows down the rate at which the coil can magnetise & demagnetise. In other words loading the primary with more resistance & less inductance reduces the time constant of the circuit.