A Practical Guide to the Ignition Coil for the 1945-1947 GMC EC152
Keep your classic GMC's ignition system reliable by understanding and choosing the right ignition coil.
- You MUST verify if your truck has a 6-volt or 12-volt electrical system before ordering a coil.
- Standard Ignition is a reliable aftermarket brand for this application, as new OEM parts are unavailable.
- Symptoms of failure include no-start, misfiring, and power loss, which often worsen as the engine warms up.
- Replacement is a simple DIY task that requires basic tools and less than an hour.
6-Volt or 12-Volt? The Most Important Question
Before buying an ignition coil for your EC152, you must know your truck's electrical system voltage. From the factory, these trucks had a 6-volt system. However, over the last 75+ years, many have been converted to a more modern 12-volt system for better starting and lighting. Installing the wrong coil can cause immediate failure or poor performance. A 6-volt coil on a 12-volt system will overheat and burn out, while a 12-volt coil on a 6-volt system will produce a very weak spark. Check your battery or use a multimeter to confirm your voltage before ordering.
Symptoms of a Failing Ignition Coil
On a classic truck with a points-style ignition, coil failure symptoms are usually very noticeable. Unlike modern cars, you won't get a check engine light, so you have to pay attention to how the engine runs. A failing coil often gets worse as it heats up.
- No-Start Condition: The engine cranks but won't fire up. This happens when the coil fails completely and produces no spark.
- Engine Misfires and Stumbles: The truck may jerk or sputter while driving, especially under load or at higher RPMs. This is caused by an inconsistent or weak spark.
- Rough Idle: The engine may shake or run unevenly when stopped.
- Backfiring: A pop or bang from the exhaust can occur when unburned fuel ignites in the hot exhaust pipe due to a missed spark.
- Loss of Power: The truck feels sluggish and weak because the cylinders aren't all firing correctly.
How to Test Your Coil
You can perform a basic test with a multimeter set to ohms. Disconnect all wires from the coil. For a 6-volt coil, the primary resistance (measured between the two small '+' and '-' terminals) should be between 1.0 and 2.0 ohms. The secondary resistance (measured between the center high-voltage tower and a primary terminal) should be between 6,000 and 10,000 ohms. Readings of zero or infinity indicate a failed coil.
Choosing the Right Aftermarket Coil
For a vehicle of this age, new Original Equipment Manufacturer (OEM) parts are no longer produced. The market consists of new aftermarket parts, used original parts, or New Old Stock (NOS). For a critical component like an ignition coil, a new aftermarket part offers the best combination of modern manufacturing, reliability, and availability.
Standard Ignition is a well-regarded brand in the aftermarket, known for producing reliable ignition components. Their products are engineered to meet or exceed original specifications, and in some cases, improve upon the original design to address common failure points. For a classic truck like the EC152, a Standard Ignition coil is a dependable choice that ensures consistent spark energy.
Ignition Coil Replacement Cost for 1945-1947 GMC EC152
| Part Category | Estimated Cost |
|---|---|
| New Aftermarket Ignition Coil | $32 - $39 |
| Shop Labor | $50 - $100 |
| Total Estimated Cost | $82 - $139 |
Cost estimates are for the part and professional installation. Prices can vary by location and shop.
Frequently Asked Questions
Do I need a ballast resistor with my new coil?
It depends on your system. A factory 6-volt system typically does not use a ballast resistor. However, if your truck was converted to 12-volts but still uses some 6-volt components (like the original points distributor), a ballast resistor is often used to reduce the voltage supplied to the coil and points to prevent them from burning out. Some 12-volt coils are designed with internal resistance and do not require an external resistor. Always follow the coil manufacturer's recommendation.
What is the difference between the two Standard Ignition coils available?
The primary difference between the available coils will almost certainly be the voltage. One will be for a 6-volt system and the other for a 12-volt system. It is critical to select the one that matches your truck's electrical system.
Is replacing the ignition coil a difficult job?
No, this is a very simple job for a DIY mechanic. The coil is typically mounted to the engine or firewall with a single bracket and has only three wire connections. The entire process usually takes less than 30 minutes with basic hand tools.
Should I replace any other parts with the ignition coil?
Yes, it's a good practice to also inspect and consider replacing the spark plugs, spark plug wires, distributor cap, rotor, points, and condenser. These components all work together in the ignition system, and a failure in one can strain the others.
Technical Specifications
System Voltage: 6V or 12V (must verify on vehicle). Ignition Type: Points-style distributor ignition. Typical 6V Coil Resistance: Primary ~1.0-2.0 Ohms, Secondary ~6k-10k Ohms.
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The information in this article is provided for general reference and educational purposes only. Vehicle specifications, procedures, and part compatibility can vary by production date, trim level, and region. Always consult your vehicle's factory service manual and verify part numbers before purchasing or performing repairs. Safety-critical components such as airbags, seat belts, and braking systems should be installed by a qualified professional.