How to Upgrade Alternator Amperage: 11 Step DIY Guide

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To upgrade alternator amperage, select a higher-output model compatible with your vehicle’s mounting and electrical system. Ensure the new alternator provides at least 20-50% more amperage to support additional electrical load. Upgrade wiring with a larger gauge to handle increased current, preventing voltage drop and overheating. Typical upgrades involve switching from a standard 100-amp to a 140-160 amp alternator, requiring 4-gauge wiring. Confirm the upgraded alternator’s pulley aligns with existing drive belts for efficient operation.

Challenges, Troubleshooting, and Solutions for Upgrading Alternator Amperage

Challenges/Issues	Troubleshooting Steps	Solutions
1. Insufficient Charging After Upgrade	Verify alternator output with a multimeter. Check belt tension and pulley alignment.	Compare the mounting points and dimensions of the new alternator with the original.
2. Overheating of Wiring	Inspect wiring gauge and connections for adequacy with increased amperage.	Upgrade wiring to a larger gauge capable of handling the new alternator’s output, typically 4-gauge for 140-160 amp units.
3. Alternator Mounting Issues	Check the electrical system for compatibility with the increased output, focusing on the voltage regulator.	Use adapter brackets if available or fabricate custom mounts to fit the upgraded alternator.
4. Electrical System Compatibility	Ensure the battery is capable of handling increased charge rates. Replace with a higher-capacity battery if necessary.	Install an alternator with a built-in regulator or upgrade the external regulator as needed to handle higher amperage.
5. Battery Not Charging Efficiently	Test battery condition and alternator charging voltage.	Ensure the battery is capable of handling increased charge rates. Replace with a higher capacity battery if necessary.

Upgrading Your Alternator: A DIY Guide to More Amps

As vehicles become more technologically advanced with additional electrical loads, the factory-installed alternator may no longer provide sufficient amperage. Upgrading to a high-output alternator is an effective solution, but can be a daunting task for the DIYer. This guide breaks down the step-by-step process for safely and successfully installing a higher amperage alternator in your vehicle.

Assessing Your Electrical Needs

The first step is determining how much additional amperage your vehicle needs. Carefully audit all electrical accessories, their rated draw, and how they’re used. Sum all amp draws and add a 25% buffer – this is the minimum amperage rating needed. An alternator should never be running at full capacity.

Image Credits: 1972 Ford XY Falcon 4WD utility by sv1ambo is licensed under (CC BY 2.0)

For example:

• 2,000-watt stereo system: 167amps
• Off-road LED light bar: 84amps
• Electric fan: 30amps
• Phone chargers/accessories: 5amps
• Total draw: 286amps
• With 25% buffer: 358amps

So a 400-360amp high output alternator would be ideal.

Choosing the Right Alternator

With amperage needs established, start researching options. Look for an alternator with the following:

• Direct bolt-on fitment
• Capable of output at low RPMs
• Built-in regulator and fan
• High-grade wiring and connections
• Good customer reviews

Also consider additional factors like pulley size, clock position, battery cables, warranties, and customer service. Settle on the best option for your budget and electrical demands.

Preparing for Installation

Once the new alternator arrives, gather all necessary additional parts and tools for installation:

• Quality insulated wrenches
• Wiring harness adapter plug (often necessary)
• Extended battery cables
• Crimp connectors
• Multimeter
• Battery charger

Take time to carefully read any instructions included with the alternator. Always disconnect the negative battery cable FIRST during automotive work to avoid shorts.

Installing the New Alternator

1. Disconnect the negative battery cable. Remove the serpentine belt and wires/connections from the factory alternator. Keep hardware for reuse.
2. Inspect the mounting area and pulley alignment system. Clean any dirt, grime, or old hardware. Use a wire brush if needed.
3. Test fit the new alternator using original bolts/brackets if possible. Check for interference issues and alignment with pulleys/belts.
4. If satisfactory, remove and mount the new alternator fully with all bolts/hardware tightened to spec using insulated wrenches.
5. Fabricate longer battery cables with crimp connectors to reach if needed.
6. Carefully wire in the new alternator system, including the regulator and harness plug if required. Use a multimeter to verify connections.
7. Reinstall all protective brackets, heat shields, and components removed during disassembly.
8. Spin the new alternator pulley by hand to verify smooth operation through a full RPM sweep.
9. Reinstall serpentine belt(s). Tension belt to factory spec if possible.
10. Reconnect the negative battery cable LAST.

Testing & Verifying Functionality

After installation, carefully test the operation before driving:

• Turn headlights and other systems on, and check the voltage output at the battery. Should be 13-14V.
• Start the vehicle, and check the output again while idling and holding RPMs at 2,500. The output should be 13.5-14.5V.
• Allow the vehicle to idle down to 500 RPM. Check voltage again, should remain steady at 13.5-14.2V.
• With a load tester, apply 50% draw and monitor voltage for at least 10 minutes. Output must remain steady.

If the voltage drops below 12.5V or fluctuates, immediately diagnose the wiring connections. Fully test and verify solid electrical operations before driving the vehicle.

Adding an Amperage Gauge

To monitor real-time amperage output, add an aftermarket gauge like a Westach 2160. Consider mounting location carefully to make readings visible while driving. An amp gauge is crucial for monitoring electrical function and identifying poorly performing accessories that may overload the system.

Maintaining Your Upgraded Alternator

With a high-output alternator installed, be diligent about:

• Monitoring amp gauge regularly
• Keeping wiring connections tight and components mounted securely as vibration can loosen things
• Adding dielectric grease annually to help prevent corrosion on terminals
• Testing for proper voltage output under load at each battery change
• Checking belt tension often, tighten or replace if slipping occurs

Prioritizing maintenance protects your investment in a high-performance alternator and electrical system. This helps ensure optimal power for all accessories and electronics.

Going from a stock 60-90amp alternator up to a 400amp high-output unit requires patience and attention to detail during installation. But the work is well worth it for modern vehicles with significant electrical draws. Follow these guidelines for smooth, reliable DIY alternator upgrades. Check back for more auto-electrical tips and tricks!