Removing an Alternator for Replacment

Here’s an article that can help describe and explain the functions of an alternator. We will also guide you through the steps and procedures for testing, diagnosing problems, and replacing a faulty alternator.

Reasons for Replacement

A majority of the time when an alternator fails, it stops charging and the battery goes dead. Other times the alternator over charges and cooks the battery. For testing and evaluating of the battery, starting, and charging system refer to the Battery, Starter, and Alternator Testing post to help with diagnosis.

Difficulty Scale

This job may not be time consuming, but there are a few steps that are critical when replacing an alternator. This skill level is more for the advanced level technician. Follow along and learn these important steps.

Tools for the Job

• 1/4″ ratchet
• 5/16″ socket
• 3/8″ ratchet
• 13mm socket
• 15mm socket
• 3/8″ extension 6″ long

Prep for Alternator Removal

Always evaluate the job before starting. Here is a view of the alternator on the left. There are 2 mounting bolts, 1 corner bracket, 1 plugin style connector, 1 nut holding the B+ wire from the battery, and the belt.

Considering that we are working with the heart of the electrical system, the first and most important thing to do is to disconnect the battery before servicing the alternator.

All side post batteries have a 5/16″ or 8mm socket size to remove the battery cable.

Important Electrical Caution!!!

Always remember, when disconnecting the battery remove the negative terminal/ground cable first!!! This is to prevent any possible contact with surrounding grounds.

If you touch a ground no problems can occur if your removing the ground cable. On the other hand, if you contact a ground while removing the positive of a live battery you can short circuit the battery and do significant damage to the vehicles electrical system.

Note: Refer to the Replacing a Serpentine Belt and Tensioner post for how to remove the belt prior to servicing the alternator.

Alternator Removal

Using your ratchet and 15mm socket, remove the upper alternator mounting bolt.

Using the 13mm socket with extension, remove the nut and the alternator support bracket from the corner of the intake manifold.

Remove the lower alternator mounting bolt.

Pull back the protective boot and remove the nut for the battery cable. This is the cable that supplies voltage to the battery when the vehicle is running.

Remove the battery cable. This is why you should disconnect the battery. Eliminate the thought of your wrench touching a ground when removing the B+ cable from the alternator.

Lift out the alternator for removal, but be aware that there is still one more wire to disconnect. The only way to reach the connector is to lift out the alternator for access.

Unplug the 2 terminal connector. This is the power and ground wires that supply the alternators voltage regulator. (More on how the alternator works later)

Install the new alternator in reverse order and retest the charging system to make sure the new alternator is working correctly.
Refer to the Battery, Starter, and Alternator Testing post for a recap on how to check for proper operation of the alternator.

Estimate for Repair

(check with your local parts stores for current prices)
Parts to replace
Using aftermarket parts you can purchase a remanufactured alternator for around $80 and a new alternator for approx. $120.
Labor to replace
This job should cost approx. 2 hr. labor to test the charging system and replace the alternator. (Example: 2hrs.@ $80)
Parts and Labor
Re-man price/ $240
New price/ $280
Note: Factory parts and shop labor rates will be higher depending on type of repair shop and location.
Time to replace
This job should take even the experienced technician approx. 1 to 1.5 hours to complete