subject: The Dis And The Coil Pack 101 [print this page] The phrase "drivers inside the DIS charge and fire the coils" has been around for years, and for many people, it is the only description of how the DIS ('distributorless ignition system' module) and coil interact that they've heard. It is easy to conclude that the DIS is charging up the coils similar to how a battery charger or generator or alternator charges up a battery, right? Electricity is fed from the alternator, as the source, into the battery as the destination, until that electricity is sent to the starter, as one example. Sounds simple enough, but in the case of the DIS and the coil(s), this conclusion paints a completely incorrect picture. The DIS doesn't supply any electricity to the coil pack. So why have we heard that it 'charges and fires'?
The 'coils' inside the coil pack are just that...coiled LCD Monitor bundles of wire, that when fed voltage generate magnetic fields. Did you ever make a magnet in school with a wire around a pencil, where you could pick up metal objects as long as some electricity was being passed through the wire? This is also where many people learned that for a 'circuit' to work, it had to be connected to a source of electricity in such a way that the electricity could flow between the positive (+) and negative (-) connections...the negative connection is commonly called the 'ground'. In England they say 'earth' - "be sure the circuit is 'earthed' "...or grounded - connected to ground means that the circuit is complete or closed.
Ok, enough of school...what about our distributorless ignition systems? In our case, there are circuits made up of primary coils and secondary coils. The primary coils are energized (on), than de-energized (off)...over and over. When their circuits USB Monitor are turned on (connected to ground), then off (disconnected from ground) their magnetic fields collapse. It is this collapse and subsequent influence on the secondary coils that results in the spark to the plugs. With me so far? Good. Moving on... Where do the coils get their electricity from and how are they turned on and off? Where's the switch? (Note that Ford loves to switch circuits on and off at the ground or negative side of a circuit, instead of at the positive side. This can make it tricky to troubleshoot circuits unless you know where to look for how the circuit is being triggered, or turned on and off.)
Stay with me. The DIS controls the primary coil circuits in the coil pack by connecting then disconnecting the ground for each primary coil. The coils are fed electricity from the wiring harness at full system voltage, called VBAT by some, which simply means 'battery voltage' - positive 12 volts (minimum)...this is simply an electrical source that isn't shaped or reduced Touchscreen Monitor by any other component. Its hot and nasty and looking for some place to run to. A wire off the engine harness feeds VBAT to the coil pack, where it is then internally sent to each coil bundle (three groups - six coils...three primary and three secondary - one of each per group. Each secondary coil is used to feed two spark plugs).
