Mechanics

Alternator Replacement

Easy step by step guide on how to replace an automotive alternator, though the appearances may vary the procedure is the same for most vehicles.

Tools and Supplies Needed

  • Replacement Alternator
  • Shop towels
Park your car on level ground with the engine off and the emergency brake "ON". If needed, raise a car according to the manufacturers recommended instructions and secure with jack stands, use a basic set of tools, wear eye protection and gloves.

Step 1 - Loosen and remove the negative battery cable, push the cable away from the terminal to avoid an accidental connection. Please Visit - Battery Removal


Remove Negative Battery Cable

Step 2 - Release the serpentine belt tensioner to remove the belt. Please visit - Removing Serpentine Belt


Remove Serpentine Belt

Step 3 - Remove the dust boot from the alternator main power terminal to expose the main power wire. (Note: If wiring is difficult to access, you will be able to disconnect the wiring once the alternator is loose.) (Note: All alternators are designed with a main power cable (large) that goes directly to the battery for charging purposes.) (Note: Some applications will require the removal of the power steering pump to access the alternator. Please Visit - Remove Power Steering Pump


Alternator Main Power

Step 4 - Using a socket remove the main power cable lead mounting nut from the alternator.


Remove Alternator Main Power Cable Mounting Nut

Step 5 - After the nut has been removed, grasp the main power cable and lift it from the alternator terminal.


Main Power Cable

Step 6 - Locate the alternator wiring harness, grasp the dust boot and pull it back enough to access the electrical connector.


Pull Dust Boot Back

Step 7 - While releasing the safety clip on the side of the connector, pull to remove the wiring harness.


Remove Wiring Harness Connector

Step 8 - After clearing any wiring or hoses, use a wrench or socket to remove the upper alternator mounting bolt and bracket.


Remove Top Mounting Bolt

Step 9 - Locate and remove the lower mounting bolt.


Remove Bottom Mounting Bolt

Step 10 - After the mounting bolts have been removed, grasp the alternator and move it back and forth, this will help release the press fit (lower mounting bracket) used to hold the alternator in place.


Move Alternator Back and Forth

Step 11 - Once the alternator becomes loose in the engine bay, gently lift to remove. (Note: This step can take some trial and error depending on application.)


Failed Alternator

Step 12 - Match the new alternator to the old unit, including electrical plug to ensure a proper installation.


Match New Alternator

Step 13 - Most alternator mounting brackets include a press fit sleeve that must be moved slightly outward to make installation possible.


Press Fit Sleeve

Step 14 - Using a large punch gently hammer the sleeve outward to allow room for the new alternator. (Note: Without this step reinstallation will be difficult.)


Punch Alternator Bracket Sleeve

Step 15 - The sleeve will look like this once moved, creating a gap in which to lower the alternator into.


Sleeve Moved

Step 16 - Gently lower the new alternator into the engine bay.


Install Alternator

Step 17 - Once the alternator is in place, reinstall the lower mounting bolt, leave it hand tight until the installation of the upper bolt, then tighten completely.


Installing Lower Mounting Bolt

Step 18 - Reinstall any brackets removed in the process.


Reinstall Bracket

Step 19 - Hand thread in the upper mounting bolt and tighten, then tighten the lower bolt as well.


Reinstall Upper Mounting Bolt

Step 20 - After all mounting bolts are tight, reinstall the wiring harness along with the rubber dust boot.


Reconnect Wiring Harness

Step 21 - Reinstall main charge cable and mounting nut, gently tighten the cable into place (do not over tighten), reinstall rubber dust boot, also, reinstall any wiring harness position clips.


Install Charge Cable

Step 22 - Check the condition of the serpentine belt, replace if needed and reinstall. Please visit - Serpentine Belt Replacement


Reinstall Serpentine Belt

Step 23 - Gently touch the negative cable to the battery post, there should be a small spark, tighten the cable end. (Note: If a large spark is generated the alternator charge cable is grounded and needs to be rechecked.) Once the job is complete the alternator operation should be tested. Please Visit - Alternator Testing


Reconnect Negative Battery Cable

Helpful Information

When an alternator fails the battery warning light will come on, the battery to lose charge causing the engine to stall and not crank over.

AUTHOR


Written by
Co-Founder and CEO of 2CarPros.com
35 years in the automotive repair field, ASE Master Technician, Advanced Electrical and Mechanical Theory.


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Article first published (Updated 2015-05-25)