Automotive Ignition Coils

Automotive Ignition Coils Come In A Wide Range Of Shapes, Sizes And Applications

The distinct differences between coil designs make identification of optional coils relatively simple for both the parts specialist and the technician.

Ignition coils come in a wide range of shapes, sizes and applications. Distributor-type, and distributorless ignition systems all rely on one or more ignition coils to transform battery voltage into the higher voltage required to jump the spark plug gap and efficiently ignite the air-fuel mixture. The distinct differences between coil designs make identification of optional coils relatively simple for both the parts specialist and the technician. While newer coil designs are often unique and very application-specific, the so-called “universal” coil still creates a good deal of confusion at the parts counter.

The canister-type coil is commonly found in breaker-point ignition systems, as well as some early breakerless systems. In addition, this coil design is popular among performance ignition manufacturers. Far from obsolete technology, these coils are still a stocking item at many parts stores, and come in two distinct types. Unfortunately, their external appearance is so similar that only the manufacturer’s labelling or a resistance (ohms) test can differentiate between the two types. Simply selecting any “universal” canister-type coil found in the catalog or on the shelf is a common mistake, often leading to ignition performance issues, unhappy customers and “defective” returns.

For 12V universal coils, there are two categories: those coils with an internal resistor, and those for use with an external resistor. This seems to be the most common source of confusion, as many customers (and some counterpeople) don’t understand the differences between the two systems. Coils with an internal resistor have a resistance value of approximately 3 ohms across the primary circuit (between the + and – terminals), while coils designed for use with an external resistor have roughly half that resistance (1.5 ohms). An external ballast resistor (like those commonly cataloged for classic Mopars) or a resistance wire contributes another 1.5 ohms to the circuit. The net effect is the same, with a 12V supply and 3 ohms of total resistance, the result is 4 amps of current flowing through the circuit. (12 volts / 3 ohms = 4 amps)

Interchanging these two types of ignition coils can have one of two very different effects on the ignition system. The use of an “internal resistor” coil in an ignition system equipped with an external resistor will cause excessive resistance in the system, leading to weak coil and spark output. In a system requiring an “internal resistor” type coil, the use of the external resistor style coil can lead to heat failure of the ignition coil. In vehicles equipped with breaker points, this can also cause premature wear/burning of the points. Using the same formula as before, with a 12V supply and only 1.5 ohms of resistance, the resulting current flow is doubled to 8 amps.

Occasionally, a customer may request a 6V coil for their classic vehicle, or possibly a vintage tractor. While the primary resistance of the correct 6V coil and the 12V external-resistor coil are similar (and I have heard of a few old-timers using them interchangeably on vintage tractors), using the 12V coil with an internal resistor can drop the current below the threshold required to fire the plugs reliably, especially at higher RPMs. Attempting to use a 6V coil in a 12V system (or a 12V coil in a 24V system) will lead to rapid coil failure, so choosing the correct coil for the application is critical. For customers considering the popular 6V to 12V conversion, be sure to recommend the appropriate 12V ignition coil along with the new battery, alternator and accessory electrical components.

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Customer Service: How It’s Done

Customer service should be your number one priority, and it all starts with the greeting.

This is always an important topic to discuss, because I consider excellent customer service one of the most important tools you can have to earn trust, respect and repeat business from the customers that come through your door. Whether that customer is do-it-yourselfer from across town or the professional repair shop across the street, your business depends on a solid relationship.It’s a subject that I am passionate about, and it’s one that many people are losing touch with. Whether you are communicating to someone in person, on the phone or using some type of social media, good customer service and bad can both exist. You can’t afford the latter, so this is the first in a series of topics which can and should be shared from the front of the shop to the back. No matter which role you hold, you represent the shop and yourself. Customer service should be your number one priority.First on the list is the greeting. From the second a customer walks in the door, they need to know you appreciate them coming in and how important they are to your business. First impressions are everything and here’s the correct way to do it each and every time: look them directly in the eye, smile and say hello!Of course, you can say “Good morning” or “Welcome to Joe’s Autocare,” but it should be a formal greeting and the most important thing is that you have smiled, looked them in the eye and recognized that they have walked through the door.You should always retain a formal greeting until you are on a first-name basis with a customer. Only once you have established that level of relationship is it OK to use the less formal greeting of “Hi,” followed by the person’s name.This greeting does more than just indicate respect and appreciation for someone walking through the door. Most likely there are customers both new and old who are in earshot of your conversation. For newer customers, this continues to build rapport and reinforce their positive view of your shop; they see that you demonstrate respect and treat everyone in the same manner. For repeat customers, even ones that have been coming for years, the greeting is important because the way you treat them is the reason they continue to come.And when a long-time customer comes in and you greet them with “Hi [First Name],” this indicates your appreciation for them and that you’re glad to see them as a person, more than just a customer. New customers that witness this will see that your repeat customers are comfortable enough to be on a first-name basis, another indication of the trust they have in you.

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