The alternator I bought from you doesn't work.

Each alternator is bench-tested before shipping. Apparent failure is usually due to ordering the wrong unit, shipping damage, or installation mistakes. Verify the part number, inspect for damage, and review the proper installation steps (Technical Tip TT-648) before contacting support.

The alternator I bought from you doesn't "put out".

Low-output symptoms are often caused by factors outside the alternator. Measure voltage directly at the rear of the unit with a digital meter; if readings seem low, check the common issues listed below or return the alternator for a free bench test.

High-output alternators ship with an overdrive pulley that may require a belt about 1 inch shorter than stock. Use a quality, oil-free belt to prevent slip and ensure full output.

Regulator plug not plugged in, not seated properly or pinched wire

Make sure the small regulator plug on the alternator is fully seated and oriented correctly. A pinched or missing connection will prevent charging. Self-exciting models (e.g., Fitzall 220A+) do not use this plug.

Battery warning light bulb in dash missing, blown or bad connection

Some vehicles rely on the dash battery-warning bulb to excite the alternator. A blown, missing, or poorly connected bulb can cause a no-charge condition.

Customer changed alternator pulley

Replacing the supplied overdrive pulley with a larger-diameter pulley slows the alternator and decreases charge output.

Vehicle crankshaft pulley diameter too small

Aftermarket under-drive crank pulleys spin accessories more slowly and can severely reduce alternator output. Ensure the crank pulley is at least OEM size.

Main vehicle charge wire too small or not upgraded

Factory charge wiring is sized for OE amperage. When loads rise, upgrade to a heavier-gauge cable such as the Big Zero kit to avoid voltage drop and false low-output symptoms.

Too many grounds, insufficient grounds, or just bad wiring

Improper, corroded, or excessive grounds-as well as undersized or poorly crimped wires-can cripple alternator performance. Have a qualified technician inspect and correct wiring.

Bad, old, weak, damaged or cheap battery

Weak or inexpensive batteries-especially some gel-cell types-may not accept the alternator's current. Use a healthy wet-cell battery with sufficient cold-cranking amps.

Alternator possibly damaged during installation

High-output units contain sensitive electronics. Skipping the recommended battery-disconnect procedure or other steps in Technical Tip TT-648 can damage the regulator and cause no-charge conditions.

The alternator I bought from you doesn't fit.

Direct-fit models require no hardware changes. Universal Fitzall 220A+ units need custom brackets and may require a shorter belt.

Do you sell brackets, spacers or hardware to mount the Fitzall on my particular application?

Due to the vast number of vehicles, PowerBastards does not supply custom mounting hardware. Most customers fabricate brackets themselves or hire a qualified shop.

I tested my alternator and it only makes 30A.

Alternators supply only the amperage the system demands. Clip-on amp meters can be inaccurate; 30 amps may be normal at low load. Send the unit in for a free certified output test if in doubt.

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High Output Alternators for GMC Medium/Heavy

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When it comes to keeping your GMC Medium/Heavy truck running strong, you can't compromise on power. High Output Alternators for GMC Medium/Heavy vehicles from PowerBastards deliver the reliable performance and durability your fleet deserves. Designed to support even the most demanding electrical systems, these alternators keep your truck ready for work at all times.

Why Choose a High-Output Alternator for GMC Medium/Heavy Trucks?

Your GMC Medium/Heavy truck does more than just drive from point A to point B — it powers lights, tools, communication systems, and other heavy-duty accessories essential for commercial operations. A high amperage alternator for GMC Medium/Heavy ensures that every critical system gets the energy it needs without draining your battery or causing electrical failures.

With a GMC Medium/Heavy high amp alternator, you'll experience a significant boost in electrical capacity. Whether you operate a Sierra HD, Savana Cutaway, or TopKick, these alternators are built to handle it all. They are the ultimate upgrade to keep your fleet dependable and your business moving.

Benefits of Upgrading to a GMC Medium/Heavy High Amp Alternator

Upgrading to a GMC Medium/Heavy high amp alternator offers multiple benefits beyond just increased power. These units:

Provide consistent voltage and power under high loads
Reduce the risk of electrical overloads
Improve battery life and overall electrical system health
Support additional accessories like upgraded lighting or onboard equipment
Enhance vehicle reliability in critical job site situations

A GMC Medium/Heavy performance alternator is specifically engineered to support extensive aftermarket upgrades. So, if you rely on advanced communication systems, large inverters, or heavy winches, this upgrade is exactly what your truck needs.

Built for Heavy-Duty Demands

Every High Output Alternator for GMC Medium/Heavy from PowerBastards is crafted to exceed industry standards. We understand that downtime is not an option when you're on the job. That's why these alternators are built to prevent electrical failures and costly repairs, keeping your fleet operational and your projects on track.

Our aftermarket alternator GMC Medium/Heavy options go through rigorous quality testing and strict control processes. Each unit is designed to perform flawlessly in extreme weather, heavy loads, and around-the-clock duty cycles.

Easy Installation and Compatibility

Our GMC Medium/Heavy alternator upgrade is engineered for a straightforward, direct-fit installation. No need for complicated modifications or downtime-consuming adjustments.

Built to work perfectly with:

Sierra HD: Delivers reliable power for heavy towing, plows, and additional job site equipment.
Savana Cutaway: Supports commercial builds and fleet vehicles with multiple high-draw accessories.
TopKick: Handles extreme electrical demands for heavy-duty vocational and service applications.

Once installed, you can immediately take advantage of improved power delivery and electrical stability. It's an upgrade that delivers real, noticeable improvements from day one.

Explore our full range of High Output Alternators for GMC Medium/Heavy trucks and equip your fleet with dependable, high-performance power built to handle any job.