A Guide to Aftermarket Alternators for the 1987 GMC V2500
Keep your classic GMC's electrical system running strong by choosing the right replacement alternator for your needs.
- Confirm your amperage needs; a stock truck is fine with a 78-94 amp unit, while added accessories require 100 amps or more.
- Replacement is a simple DIY job for most owners, requiring only basic hand tools and about an hour of time.
- Before replacing the alternator, check all battery cables and ground connections, as poor connections are a common issue on these trucks.
- For high-output alternators (120A+), plan to upgrade the main power and ground wires to handle the increased electrical load safely.
Is Your Alternator Failing? Common Symptoms
The alternator on a 1987 V2500 is a straightforward component, but when it starts to fail, it can cause a variety of electrical issues. Because these trucks have simpler electrical systems, the signs are often very clear.
- Dimming or Flickering Headlights: This is one of the most common signs. You might notice your headlights seem dim at idle and brighten up when you rev the engine.
- Battery Warning Light: Your dashboard has a "GEN" or battery-shaped warning light that will illuminate if the alternator's output is too low.
- Weak or Dead Battery: A bad alternator can't recharge the battery, leading to slow engine cranking or a truck that won't start at all, even with a relatively new battery.
- Whining or Growling Noises: Worn-out bearings inside the alternator can produce a distinct whining or growling sound that changes with engine RPM.
- Electrical Accessory Problems: You might notice the radio cutting out or the blower motor for your heater running slower than usual.
Check Your Connections First
Before replacing your alternator, always check for simple issues. On these classic GM trucks, a loose or corroded battery cable, a bad ground wire, or a loose main charge wire at the back of the alternator can cause charging problems that mimic a failed unit.
Choosing the Right Aftermarket Alternator
When shopping for a new aftermarket alternator, the most important factor is your truck's electrical needs. Your choice will fall into one of three categories.
1. Standard Replacement (78-100 Amps)
If your V2500 is mostly stock without major electrical accessories, a standard replacement is all you need. These are designed to meet or slightly exceed the original factory output. Look for units in the 78 to 100-amp range, which was a common factory option for trucks with more equipment.
Brands in this tier: BBB Industries, MPA, WAI Global, Remy
2. Premium Replacement (100+ Amps)
For owners who want extra peace of mind and proven durability, a premium-quality new alternator is a great choice. These often feature higher-quality internal components and undergo more rigorous testing than budget options. Bosch is a well-regarded brand known for supplying original equipment to many manufacturers.
Brands in this tier: Bosch
3. High-Output (140+ Amps)
If you have added or plan to add power-hungry accessories like a winch, powerful off-road lights, or a large audio system, a high-output alternator is necessary. These units can produce significantly more amperage at both idle and higher RPMs to keep up with the demand.
Brands in this tier: Powermaster, Proform
Pro Tip: Upgrading to High-Output
When installing a high-output alternator (typically anything over 120 amps), it is highly recommended to also upgrade your truck's main wiring. This is often called the "Big 3 Upgrade" and involves replacing the alternator-to-battery wire, the battery-to-ground wire, and the engine-to-ground wire with thicker gauge cables. This ensures the extra power can flow safely and efficiently.
Cost of a New Aftermarket Alternator for a 1987 GMC V2500
| Part Type | Estimated Cost |
|---|---|
| New Aftermarket Alternator | $47.17 - $262.86 |
| Shop Labor | $100 - $200 |
Frequently Asked Questions
Can I replace the alternator on my 1987 V2500 myself?
Yes, this is a very DIY-friendly job. The alternator is located at the top of the engine and is easy to access. The process involves loosening the mounting bolts to slacken the V-belts, removing the electrical connections and bolts, swapping the unit, and re-tensioning the belts. The entire job can typically be done in about an hour with basic hand tools.
What amperage do I need?
For a stock truck, a 78-amp or 94-amp unit is a safe bet and a common factory size. If you have added electrical accessories like lights or a stereo, consider an alternator with 100 amps or more. If you have heavy-duty equipment like a winch, a high-output model of 140 amps or more is recommended.
What is the difference between a 1-wire and a 3-wire alternator?
Your factory V2500 uses a 3-wire setup. This includes the main battery charge wire and a 2-wire plug that senses voltage and triggers the warning light. Some high-output aftermarket alternators are "1-wire" units that only require the main battery charge wire to be connected, simplifying the wiring. For a stock replacement, sticking with the factory 3-wire design is easiest.
Do I need to change the pulley on the new alternator?
Usually not, but always check. Your 1987 V2500 uses a V-belt system. Make sure the new alternator comes with a single V-belt pulley. If it comes with a serpentine or double V-belt pulley, you will need to swap it with the pulley from your old alternator.
Technical Specifications
OEM Part Numbers: 1101110 1101111 1105688 1105710 1105711 1105712
The 1987 GMC V2500 typically uses a Delco 10SI or 12SI style alternator with an internal voltage regulator and a single V-groove pulley. Common factory amperage ratings include 78A and 94A.
We Have This Part in Stock
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.
- GMC V2500:
- 🛍️ Shop This Part
- Is Your Alternator Failing? Common Symptoms
- Check Your Connections First
- Choosing the Right Aftermarket Alternator
- 1. Standard Replacement (78-100 Amps)
- 2. Premium Replacement (100+ Amps)
- 3. High-Output (140+ Amps)
- Pro Tip: Upgrading to High-Output
- Cost of a New Aftermarket Alternator for a 1987 GMC V2500
- Frequently Asked Questions
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