Your Guide to the Best Alternator for a 1979-1987 GMC C1500 Suburban
Keep your classic GMC's electrical system running strong by choosing the right new aftermarket alternator.
- An alternator replacement is a simple, DIY-friendly job on these trucks that takes 1-2 hours.
- Consider upgrading from the stock 63-amp alternator to a 94-amp unit for better performance, even on a stock truck.
- If you install a high-output alternator (94A+), you must also upgrade the main charge wire to a heavier gauge to prevent a fire risk.
- Before replacing the alternator, always test the battery and check for clean, tight cable connections to rule out simpler problems.
Is Your Alternator Failing? Common Symptoms
An alternator rarely fails without warning. For your 1979-1987 GMC C1500 Suburban, the signs are usually straightforward. Because the electrical system is simpler than in modern trucks, you can often spot the problem early.
- Dim or Flickering Lights: The most common sign. You may notice your headlights and dash lights are dim at idle and might brighten when you rev the engine.
- Battery Warning Light: Your dash might have a "BATT," "GEN," or battery-shaped light. If this light comes on and stays on, it's a direct warning that the charging system has a problem.
- Whining or Grinding Noises: A high-pitched whine or a grinding sound coming from the front of the engine can signal failing bearings inside the alternator.
- Weak or Dead Battery: The alternator's job is to recharge the battery. If the alternator is weak, your battery will drain while you drive, eventually leaving you unable to start the engine.
- Slow Electrical Accessories: You might notice your power windows operate more slowly than usual or your radio has issues. This is a sign of low system voltage from a weak alternator.
Don't Mistake a Bad Battery for a Bad Alternator
Before you replace your alternator, make sure your battery is in good health and the battery cable connections are clean and tight. A weak battery or corroded terminals can mimic alternator failure. Most auto parts stores can test both your battery and alternator for free.
Choosing the Right Aftermarket Alternator
For a vehicle of this age, new OEM parts are generally not a practical option. The aftermarket offers excellent choices that often exceed the original 1980s quality and performance. The main decision you'll make is about power output, measured in amps.
Stock vs. High-Output Amperage
Original alternators for these Suburbans were often rated around 63 amps. This is enough for a stock truck with no added electronics. However, if you have added or plan to add accessories, you should upgrade.
- Standard Output (63-78 Amps): A good choice for a stock or lightly modified truck. It will run the vehicle perfectly fine as it was originally designed.
- Medium Output (94-105 Amps): This is a popular and smart upgrade. It provides plenty of power for modern additions like a better stereo, brighter headlights, or an electric fuel pump without straining the system. The Delco 12SI style alternator is a common bolt-in upgrade from the original 10SI.
- High-Output (140+ Amps): Choose this only if you have significant electrical loads, such as a powerful audio system with amplifiers, off-road lights, a winch, or an electric fan conversion.
Upgrade Your Wiring with a High-Output Alternator
If you install an alternator with a significantly higher amperage (94 amps or more), you must also upgrade the main charge wire that runs from the alternator to the battery. The factory wire is too small and can overheat, creating a fire hazard. An 8-gauge or even 4-gauge wire is recommended for these upgrades.
Brand Tiers for Your Suburban
- Premium High-Output: Brands like Powermaster and Proform specialize in high-amperage alternators. They are built for performance and can handle heavy electrical loads, but come at a higher price.
- OEM-Style Replacements: ACDelco, Bosch, and Remy are trusted names that offer new and remanufactured alternators that meet or exceed factory specifications. An ACDelco or Remy unit is a reliable choice for most owners looking for dependability.
- Value-Focused: Brands like BBB Industries, MPA, and WAI Global offer cost-effective solutions. Many of these are available at local auto parts stores and often come with a lifetime warranty, which can be a major advantage for a daily-driven vehicle.
Typical Replacement Costs
Replacing the alternator on a 1979-1987 C1500 Suburban is a common repair. The part itself is affordable, and labor costs are low due to easy access.
| Item | Estimated Cost |
|---|---|
| New Aftermarket Alternator | $47 - $263 |
| Shop Labor | $100 - $250 |
| Total Estimated Cost | $147 - $513 |
Costs are estimates and will vary based on your location, the specific part chosen, and your vehicle's condition.
Frequently Asked Questions (FAQ)
Is it hard to replace the alternator myself?
No, this is a great DIY job for beginners. The alternator is usually mounted at the top of the engine and is easy to reach. The process involves disconnecting the battery, loosening the drive belt, removing a couple of bolts and wires, and then swapping the part. The entire job can typically be done in 1 to 2 hours with basic hand tools.
Do I need a higher amperage alternator?
If your truck is completely stock, you don't necessarily need one. However, upgrading from the original 63-amp unit to a 94-amp 12SI model is a common, affordable, and beneficial improvement that gives you a larger power reserve for cleaner-running electronics and a healthier battery. If you have added a modern stereo, fuel injection, electric fans, or extra lighting, a higher-amperage alternator is strongly recommended.
What is a "one-wire" alternator?
A one-wire alternator is a simplified aftermarket design that only requires the main battery charging wire to be connected. The factory setup uses a small plug with two or three wires for the voltage regulator and warning light. While one-wire units are popular for custom builds due to their clean look, using a standard plug-in replacement ensures your factory battery warning light will function correctly.
Are there any recalls or known issues?
There are no major recalls or Technical Service Bulletins (TSBs) from GM related to the alternator on these trucks. The charging system is simple and reliable. Most failures are due to the age and wear of the original components.
Technical Specifications
OEM Part Numbers: 1100137 1100143 1100144
Common Factory Style: Delco 10SI. Common Upgrade Style: Delco 12SI. Common Amperage Ratings: 63A, 78A, 94A, 105A. Voltage: 12V. Regulator: Internal.
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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.
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- Is Your Alternator Failing? Common Symptoms
- Don't Mistake a Bad Battery for a Bad Alternator
- Choosing the Right Aftermarket Alternator
- Stock vs. High-Output Amperage
- Upgrade Your Wiring with a High-Output Alternator
- Brand Tiers for Your Suburban
- Typical Replacement Costs
- Frequently Asked Questions (FAQ)
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