A Guide to Aftermarket Alternators for the 2004-2015 Subaru Impreza
Keep your Impreza's electrical system running strong by understanding common alternator problems and how to choose the right replacement.
- Alternator failure symptoms include dim lights, a dashboard warning light, a dead battery, and whining noises.
- Replacement is a feasible DIY job for many owners, taking 1-2 hours, due to the alternator's accessible top-engine location.
- Always match the amperage of the new alternator to your Impreza's specific model (base vs. WRX/STI) to ensure proper function.
- High-quality aftermarket brands like Bosch, ACDelco, and Remy offer a reliable alternative to more expensive OEM parts.
Understanding Alternator Failure in Your Impreza
The alternator is a hard-working part, and its failure can cause a cascade of electrical problems. In the 2004-2015 Subaru Impreza, which uses a boxer engine, the alternator is typically located on the top of the engine, making it relatively accessible. However, its components can wear out over time from heat and use. Common points of failure include worn-out internal bearings, which cause a whining or grinding noise, and failure of the internal voltage regulator, which leads to improper charging. Fluid leaks 🎬 Watch: Top signs and causes of Subaru alternator failure explained from other engine components, like power steering fluid or oil, can also drip onto the alternator and cause it to fail prematurely.
Symptoms of a Failing Alternator
- Dimming or Flickering Lights: Headlights and dashboard lights may dim, flicker, or appear yellowish, especially at idle.
- Warning Lights: The battery-shaped warning light on your dashboard is a direct indicator of a charging system problem.
- Electrical Gremlins: You might experience strange issues like slow power windows, a radio that cuts out, or other electronic accessories acting erratically.
- Weak or Dead Battery: An alternator that isn't charging properly will cause the battery to drain while you drive, leading to a car that won't start. If you need to jump-start your car frequently, the alternator is a likely suspect.
- Strange Noises: A whining, grinding, or growling sound from the engine bay that changes with engine RPM often points to failing alternator bearings.
- Stalling: In some cases, a failing alternator can't provide enough power to the ignition system, causing the engine to sputter or stall.
Choosing the Right Aftermarket Alternator
When replacing your Impreza's alternator, you have several options. While an OEM (Original Equipment Manufacturer) part from Subaru is a guaranteed fit, high-quality aftermarket parts can offer similar performance at a better price. Aftermarket brands often supply parts to vehicle manufacturers, so the quality can be very high. Here’s a look at some available brands:
- Bosch: Often considered a top-tier brand, Bosch is a major OEM supplier known for high-quality, reliable, and durable parts. They are a strong choice for a new or remanufactured alternator.
- ACDelco: As GM's parts division, ACDelco has a reputation for quality and offers parts for many vehicle makes, including Subaru. They are a reliable option.
- Remy: With a long history in automotive electrical systems, Remy is a respected brand offering both new and remanufactured alternators.
- BBB Industries & MPA (Motorcar Parts of America): These brands are major suppliers in the aftermarket, often focusing on remanufactured parts that meet or exceed original specifications.
Pro Tip: Always verify the amperage (Amps) of the replacement alternator matches your vehicle's requirements. WRX and STI models often require higher-output alternators than the base Impreza. Using an underpowered alternator can lead to premature failure and electrical issues.
Cost of Replacing a Subaru Impreza Alternator
The cost can vary significantly based on the part you choose and whether you perform the labor yourself. The replacement is considered relatively easy for a DIY mechanic due to the alternator's accessible location.
| Item | Estimated Cost |
|---|---|
| New Aftermarket Alternator | $43.95 - $421.55 |
| New OEM Alternator | $430 - $900+ |
| Shop Labor | $100 - $250 |
| Total Professional Replacement | $585 - $850+ |
Frequently Asked Questions
Is replacing the alternator a DIY job?
Yes, for many owners. The alternator on the 2004-2015 Impreza is located on top of the engine and is easy to access. The job requires basic tools like 10mm and 12mm sockets and involves disconnecting the battery, loosening the belt tensioner, removing the belt from the pulley, and unbolting the alternator. The entire process can take between 30 minutes to 2 hours 🎬 See this walkthrough for Subaru Impreza alternator removal and installation for a first-timer.
What's the difference between a new and a remanufactured alternator?
A new alternator is made from all-new components. A remanufactured alternator has been completely disassembled, cleaned, and inspected. Wear-prone components like bearings, brushes, and the voltage regulator are replaced with new parts, and the unit is tested to ensure it meets original specifications. High-quality remanufactured units from reputable brands can be a reliable and cost-effective option.
Do I need a special alternator for my WRX or STI?
Yes, most likely. Turbocharged models like the WRX and STI typically have higher electrical demands and are equipped with higher-amperage alternators from the factory. It is critical to install an alternator with the correct amperage rating for your specific model to avoid electrical problems and premature part failure.
How do I test my alternator?
A simple way to test your alternator is with a multimeter. With the engine off, a healthy battery should read between 12.4 and 12.7 volts. Start the engine; the voltage at the battery terminals should rise to between 14.2 and 14.7 volts. If the voltage is low or doesn't increase with the engine running, your alternator is likely failing. Many auto parts stores also offer free battery and alternator testing.
🎬 Watch: A simple guide on how to test your alternatorAre there any recalls or TSBs for the Impreza alternator?
Searches did not find any specific recalls for the alternator on 2004-2015 Subaru Impreza models. The primary recalls for this period relate to Takata airbags. While some Technical Service Bulletins (TSBs) exist for other models regarding alternator issues causing false misfire codes, these were not specific to the 2004-2015 Impreza range.
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Technical Specifications
OEM Part Numbers: 23700AA541 23700AA5418A 23700AA720 23700AA721 23700AA570
Amperage varies by model and trim, typically ranging from 90A for base models to 110A or higher for turbo (WRX/STI) models. Voltage should be 14.2-14.7V when running. The alternator is driven by a serpentine belt and has a multi-groove pulley.
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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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