Troubleshooting / Frequently Asked Questions

Some of our high-output alternators are equipped with an overdrive pulley to improve charging performance at low RPM. Because this pulley may be slightly smaller in diameter than your factory pulley, in certain vehicles the original belt may be slightly too long.

In most cases, if your existing belt is the correct length and is not stretched or worn, it will fit without issue. Only occasionally is a shorter belt required.

If a shorter belt is needed, it is typically about 1/2" to 1" shorter than your current belt. Your local auto parts store can easily supply the correct size. Keep in mind that belts are sold by length, not by vehicle make or model so if you do need a shorter than expected belt they are not hard to pick up at your local auto parts store.

As with any high-output alternator installation, we recommend using a high-quality belt and ensuring all pulleys are clean and free of oil or grease. A GOODYEAR Gatorback Poly-V serpentine belt or GOODYEAR V-belt (depending on your application) are excellent choices. ACDelco has also recently released a heavy-duty belt (green in color) that offers excellent traction and is well-suited for high-output alternator applications.

If you purchased a direct-fit high-output alternator, be sure the regulator plug on the rear of the alternator is properly connected. This plug is required for correct alternator operation on most vehicles.

Common installation issues we see include the plug not being fully seated, being forced in incorrectly, installed backwards, or having a wire pinched during installation. Any of these conditions can prevent the alternator from charging or cause it to charge at the wrong voltage. Always confirm that the plug on the new alternator matches the plug from your original alternator and that it is fully and correctly connected.

Note: If you ordered a self-exciting alternator (such as the Fitzall 220A+), the regulator plug may not be used. On these units, the regulator port is typically filled with silicone. If your alternator has the plug filled with silicone, the only required rear connection is the main battery positive cable.

Some vehicles rely on the battery warning light in the instrument cluster to activate (or “excite”) the alternator. If this bulb is blown, missing, or not functioning, the alternator may not charge at all.

This situation is very common on vehicles that have been upgraded to a custom or aftermarket dash, such as Dakota Digital systems. Many of these dashes do not use a traditional battery warning light, or the light is not present or wired the same way as the factory setup. When the warning light circuit is missing or inactive, it can result in a no-charge condition.

If you are experiencing a charging issue, always verify that the battery/charging warning light circuit is present and functional, and that the light illuminates during key-on, engine-off operation.

Changing the supplied alternator pulley to one with a larger diameter can result in lower-than-expected charging output, especially at low RPM.

We have seen cases where customers replace the installed pulley with a larger pulley they already have on hand. Increasing the alternator pulley diameter reduces alternator speed, which directly decreases charging output. For best performance, the alternator should be operated with the supplied pulley or one of equivalent diameter.

Many aftermarket products are marketed as performance upgrades, even though they may not be necessary—or beneficial—for your vehicle. One common example is an underdrive crankshaft pulley.

The crankshaft pulley is the main drive pulley at the bottom of the engine and is responsible for driving accessories such as the alternator, air conditioning compressor, and power steering pump. An underdrive pulley uses a smaller diameter to slow accessory speeds in an attempt to free up engine horsepower.

While this may offer minimal gains in some applications, reducing the crankshaft pulley diameter also significantly reduces alternator speed and output. When the crankshaft pulley diameter is decreased, alternator charging performance—especially at idle and low RPM—can be severely reduced.

We’ve covered this topic in more detail in a blog article on underdrive pulleys and charging system performance, which explains the real-world effects and tradeoffs in depth. We recommend reviewing it if you are considering or already running an underdrive crankshaft pulley.

For proper alternator performance, the crankshaft pulley should be at least the OEM factory diameter. If you are experiencing low or inconsistent charging output, we strongly recommend measuring your crankshaft pulley to confirm it has not been underdriven.

Almost all OEM charging-system wiring is not sized to support the demands of a heavily loaded high-output alternator.

For example, a vehicle such as a Chevy Malibu may have come from the factory with a 105-amp alternator. The main charge wire installed by the manufacturer was designed to safely carry approximately 105 amps from the alternator to the fuse box, main power distribution points, and ultimately the battery.

While a high-output alternator may physically bolt in and appear to function using the factory wiring, problems can arise once electrical demand increases—such as when running aftermarket audio systems or other high-amperage accessories. In these situations, the original charge wire was simply never designed to handle the increased current, which can lead to voltage drop, reduced output, or inconsistent charging performance.

To address this limitation, we offer an upgraded charging wire kit, commonly referred to as the BIG ZERO wire upgrade, specifically designed for high-output alternator applications. When running high-demand accessories such as audio systems, auxiliary lighting, winches, or other electrical loads, this upgrade is highly recommended and is often just as important as the high-output alternator itself.

Important Note: Installing a high-output alternator on an otherwise completely factory vehicle—without aftermarket audio systems or additional electrical accessories—is perfectly safe. In these cases, the alternator will not be forced to produce excess current, and skipping the BIG ZERO wire upgrade will not cause any issues under normal operating conditions.

Yes, you read that correctly—the BIG ZERO wire kit is not always necessary. It is the addition of aftermarket high-drain accessories (such as stereos, lights, and winches), not the high-output alternator alone, that creates the need for upgraded wiring.

Fun Fact:
At one point, we removed 36 pounds of unnecessary wiring from a particularly problematic Buick Regal (sorry, Jake), and every electrical issue disappeared. Less really can be more when it comes to vehicle wiring.

Improper wiring is one of the easiest ways to severely limit the performance of any alternator—especially a high-output unit.

We regularly see charging issues caused by undersized wiring, poor or loose connections, incorrect terminals, or excessive grounding. Any one of these problems can prevent an alternator from functioning correctly.

It’s important to understand that adding ground wires indiscriminately can actually create new problems. Excessive or unnecessary grounding can introduce ground loops, which may lead to electrical noise in speakers, charging irregularities, intermittent voltage behavior, and significantly more difficult troubleshooting.

Most modern vehicles already use a chassis-grounded electrical system, where the frame or unibody serves as a common ground. When factory ground points are intact, clean, and corrosion-free, adding multiple extra ground straps—often promoted online under the “Big 3” religion—typically provides little to no real-world benefit and can complicate the electrical system rather than improve it.

Instead of cluttering the engine bay with redundant wiring, our BIG ZERO Wire Kit focuses on upgrading the primary current paths that actually matter. By properly sizing and improving the main charge wire path, the system delivers cleaner voltage, improved stability, and better overall charging performance—without unnecessary complexity. Less money, less weight in your vehicle and less problems longterm.

If your vehicle has been modified or custom-wired and you are experiencing charging issues, we strongly recommend having the system inspected by a reputable, experienced automotive electrical shop. Wiring problems can be especially difficult to isolate because they often appear intermittently, such as when components heat up, after extended drive time, or only during certain vibration conditions.

We do not sell batteries, but we regularly see charging-system issues related to battery selection.

In our experience, premium gel-cell and AGM batteries—often marketed by color or brand—do not offer advantages for most street-driven vehicles and frequently introduce unnecessary complications. These batteries often cost significantly more yet tend to have a shorter service life when installed in vehicles not designed for them.

The most common reason for this reduced lifespan is chronic undercharging. Unless the vehicle was originally designed for an AGM or gel-cell battery, the vehicle’s computer (PCM) is typically calibrated for a traditional flooded battery. As a result, these newer battery chemistries are not charged correctly, which leads to underwhelming battery performance and premature failure.

Unless your application specifically requires side-mounted installation, extreme vibration resistance, or specialized use such as off-road racing or severe-duty environments, AGM and gel-cell batteries are generally not recommended. Other situations where a different battery could be used in a vehicle not designed for it includes modifying the programming in the vehicles PCM to adjust alternator output settings. Most customers and DIYer's aren't interested in this and most times it's not even possible.

It’s also important to note that unless your vehicle manufacturer originally equipped the vehicle with an AGM battery, the charging system and onboard electronics may not be fully compatible with that battery type. Many modern vehicles use charging strategies tailored to the factory-installed battery chemistry, and deviating from that design can cause improper charging behavior, electrical irregularities, and shortened battery life.

For the majority of vehicles, a traditional flooded (wet-cell) lead-acid battery provides the most reliable and consistent performance. The most important specification to look for is cold cranking amps (CCA)—the higher the CCA rating, the better the battery can support electrical demand while maintaining stable system voltage.

Always replace your battery with the same type originally specified by the manufacturer and choose a quality unit with sufficient CCA. In real-world use, this approach consistently delivers better reliability and longevity than switching to a more expensive or “high-end” battery design.

Yes, it's possible and it happens more than you think. Modern, high-quality high-output alternators can be more sensitive to electrical spikes than older or OEM alternators. This is because today’s high-output units contain significantly more onboard electronic circuitry and control components than their older, largely analog counterparts.

While this advanced circuitry enables superior charging performance and efficiency, it also means the alternator is less tolerant of improper installation or testing procedures. For this reason, it is critical that alternator removal and installation be performed in the correct sequence.

There's a specific order in hooking things up these days. Please refer to Technical Tip TT-648 for the proper alternator installation and removal steps. Failure to follow this procedure can damage the ASVR (All Silicon Voltage Regulator), potentially resulting in a no-charge or partial-charge condition.

Additionally, the outdated practice of disconnecting the battery while the engine is running to “test” alternator output should never be performed. This method will almost certainly cause regulator damage and can also harm other vehicle electronics.