In this video Bob takes a look at the Harley Davidson ignition coil. The coil consists of two winding’s of wire, the primary and the secondary. The primary receives 12 volts from the motorcycle and allows voltage to build; transferring voltage to the secondary winding where voltage is increased to thousands of volts and released through the spark plug wires to the spark plug. The primary is the area on the Harley Davidson ignition coil where the wires from the motorcycle’s harness are connected. The secondary of the coil is the area/towers where the spark plug wires plug in.
There are two types of coils used on most Harley-Davidsons. Dual fire and single fire. Dual fire coils send spark to both cylinders, all the time. Regardless of which cylinder is on the compression stroke. Single fire coils designate spark to only the cylinder that is on the compression stroke. Spark is delivered to one cylinder at a time.
Harley Davidson Ignition Coils are known to fail. The longevity you get from your coil may depend on usage, demand on the coil or environmental conditions. The coil’s capacity may diminish over time, or simply stop functioning at once. If it is determined that your motorcycle has no spark; do not just assume that the problem is your coil. There may be an underlying issue. You may have a dead short effecting voltage delivery to your coil. You may have a bad sensor, ECM or TSSM. There are a number of reasons you may not have spark from your ignition. Before condemning a coil, you should refer to the electrical manual for your year, make, and model motorcycle. The manual will instruct you on how to correctly test your coil and it’s corresponding harness.
There are different coils for different year/model motorcycles. The specified ohms resistance for the primary of a 2000 carbureted Softail will not be the same as the primary of a 2005 Ultra. It is important to use the correct electrical manual for your ride. When testing your Harley Davidson ignition coil you will be testing ohms resistance. You will find that the primary resistance will be a low number; 0.5 to 5 ohms, for example. The secondary resistance will be in the thousands of ohms. Understanding what your coil does and how it works is important for diagnosing electrical issues on your motorcycle. The ignition coil is a vital part of your Harley Davidson electrical system.