Ignition systems in older cars rely upon a condenser to control the electric charge that runs through them when activated. Newer cars have diodes to control this charge, so they don’t need condensers. The ignition system contains two circuits in an ignition coil to carry the current. When the current passes from one circuit to the next, the magnetic field around the first one drops and subsequently paves the way for a high voltage spike. It is the job of the condenser to minimise these spikes to protect the ignition system. You can tell if your condenser is failing if your ignition starts to spark – an early sign of this is unusual static in your radio transmission. If a faulty condenser is left unrepaired for too long, the sparking will cause more lasting damage to other parts in your ignition system.