What to Do After Replacing Alternator: 7 Facts to Remember!

Reviewed by Dr. Deepakkumar Jani

After replacing an alternator, verify installation accuracy, reconnect the battery, ensure belt tension is correct (ideally 1/2 inch deflection for most models), and check electrical connections for tightness and corrosion. Start the vehicle and measure alternator output with a multimeter (expect 13.5-14.5V across battery terminals at idle). Inspect for unusual noises indicating improper installation. Finally, reset any fault codes that may have been triggered and conduct a road test to confirm normal operation.

Troubleshooting for Post-Alternator Replacement

Challenge/IssueSymptomsTroubleshooting StepsSolution
Incorrect Alternator Output– Low/high voltage reading1. Verify belt tension
2. Check wiring connections
Adjust belt
Repair wiring
Battery Not Charging– Battery light on – Slow engine start1. Test battery condition
2. Measure alternator output
Charge/replace battery Recheck alternator output
Noise After Installation1. Test battery condition
2. Measure the alternator output
1. Inspect belt alignment 2. Check the pulley and bearingsAlign belt
Replace defective components
Electrical System Errors– Erratic instrument behavior1. Reset the vehicle’s ECU
2. Check for loose connections
Reset ECU
Secure all connections

After Replacing Your Alternator: The Next Crucial Steps

You’ve successfully replaced your vehicle’s worn-out or damaged alternator. Congratulations! But the repair doesn’t stop there. Taking the proper post-replacement precautions is crucial for restoring full electrical function and preventing premature alternator failure. As an alternator DIYer, this guide has the step-by-step specifics you’re looking for.

What to Do After Replacing Alternator

Image Credits: Water cooled alternator by Chris Bede is licensed under (CC BY 2.0)

Follow These 7 Key Steps to Ensure Alternator Durability and Performance

Double Check All Electrical Connections

Before starting the engine, visually and physically check that all electrical connections have been tightly secured. Pay special attention to:

  • Battery terminals
  • Alternator wiring harness plugs
  • Mounting bolts (torque to OEM specifications)

Loose battery cables and alternator wiring allow damaging voltage spikes during charging. And an even slightly loose drive belt can inhibit proper battery charging.

Reconnect the Battery and Check the Voltage

Reconnect the battery terminals and start the engine. Using a handheld voltmeter, check the voltage across the battery posts with the engine at 1500 RPM. The charging system voltage should be between 13.7–15.2 volts. Any readings outside this range may indicate:

  • Faulty voltage regulation
  • Defective rectifier bridges or stator windings
  • Ground connection issues

If voltage fluctuation persists, immediately shut off the engine and investigate the source of the electrical abnormality. Leaving a dysfunctional charging system unchecked will fry electronics and leave you stranded.

Let Idle and Scan for Warning Lights

Allow the engine to return to a stable idle. Carefully monitor the dash for the “Check Charging System” warning light or battery/alternator warning indicator. Warning lights coming on or flickering usually stem from loose wiring connections or belt slippage.

However, this may also indicate diodes and stator windings were severely damaged by the failed alternator. Have the check engine computer scanned at an auto parts store to pinpoint any diagnostic trouble codes (DTCs). Address any electrical issues before continuing normal vehicle operation.

Inspect Serpentine Belt

As engine RPMs settle, visually check the serpentine belt driving the new alternator. The belt should have proper tension with no visible cracks or deteriorated rubber. Inadequate tension prevents the alternator from receiving the full rotor RPMs needed to generate electricity.

While idling, spraying the belts with water from a spray bottle can help identify slipped belts. Squealing or faster spinning sounds signal poor grip. Tighten or replace belts accordingly.

Load Test New Alternator

The true test of alternator effectiveness and reliability comes under electrical load. To confirm proper operation, use an automotive battery/charging system analyzer or voltmeter to run an alternator diode ripple test and voltage load test.

The diode ripple test checks that stator diodes effectively convert AC voltage to DC. Excess voltage ripple confirms shorted or damaged diodes. A voltage load test checks the alternator can maintain steady system voltage when handling battery charging and heavy electrical loads like headlights, fans, etc.

If the new alternator passes both tests while under engine load, you can rest assured charging capacity and current handling is up to standards.

Fixed Battery Damage

A failing or failed alternator forces the battery into overtime. The battery’s plates become increasingly sulfated from chronic undercharging. Excessive discharge often leads to permanent battery capacity loss.

To prolong battery lifespan:

  • Use a memory saver to prevent computer memory loss
  • Fully recharge the battery before reconnection
  • Load test the battery to determine if replacement is required

A marginal battery will fail sooner rather than later even with a perfectly functioning charging system. Replace compromised batteries right away.

Practice Preventative Maintenance

Once the new alternator installation checks out, be diligent about maintenance to achieve the longest lifespan possible.

  • Maintain proper belt tension
  • Check battery terminal tightness
  • Load test the alternator annually
  • Fix minor electrical issues immediately
  • Consider voltage monitoring/recording devices

Following these post-replacement steps allows your new alternator to operate at peak charging performance for years. Stay ahead of typical failure points through vigilance and preventative maintenance. Don’t allow your DIY alternator replacement hard work to be in vain.

In summary, once an alternator replacement is complete in your vehicle:

  1. Double check all electrical connections are tight before starting the engine
  2. Reconnect the battery, start the vehicle, and test the voltage output to identify any lingering charging issues
  3. Allow the engine to idle, watching for warning lights indicating loose connections
  4. Inspect the serpentine belt for proper tension and condition, adjusting or replacing as needed
  5. Use electrical system analyzers to load test alternator operation and confirm sufficient charging capacity
  6. Load test the battery, fully recharge, and replace it if necessary
  7. Make alternator-focused preventative maintenance a regular practice

Following this structured plan for post-replacement confirmation ensures your new DIY alternator achieves peak, reliable performance. Identifying and addressing electrical abnormalities quickly is the key to longevity. Don’t overlook these crucial steps. Empower yourself by understanding the intricacies of your vehicle’s charging system.