Owners of other Toyota, Lexus or Scion vehicles such as the Yaris, Matrix, Prius, Camry, RAV4, Sienna, Tacoma, Tundra, FJ Cruiser, Venza, Highlander, Avalon, Sequoia, Land Cruiser, Allion, Premio, Auris, IS 250, ES 350, GS 350, tC, xB, xD, iQ and FR-S may also find these DIY instructions to be helpful.

The most common symptoms of a failing alternator include headlights that dim or flicker, a whining or growling sound, difficulty starting the engine (even with a new or good 12V battery), slow power windows, a burning rubber smell, an electrical burning smell, stalling, a weak or dead 12 volt car battery, rough idling and a battery warning icon on the gauge cluster.

The OEM (original equipment manufacturer) alternator in this 2010 Corolla S was part number Toyota 27060-0T041 also known as Denso TN104210-5491.

A few other compatible replacement aftermarket alternators with their part numbers include the following: TYC 2-11577, Remy 12897, Denso 210-0731 and Denso 210-0699.

The tools needed to complete this procedure include a 10mm socket, a 1/4" drive ratchet, a 12mm socket, a 14mm socket and a 3/8" drive ratchet.

The first two steps are to open the hood and then pull off the plastic engine cover.

Set the cover aside in a safe place.

Loosen the nut on the negative "-" terminal nut by turning it in the counterclockwise direction with the 10mm socket and a 1/4" drive ratchet.

Wrap the terminal in a small towel and tuck it away on the right side of the battery to help prevent accidental electrical contact.

Attention: Please make sure the "-" negative 12V battery terminal has been disconnected before continuing this procedure!

I chose to use a blue Sharpie marker to mark the current position of the belt tensioner bolt.

Loosen the long belt tensioner bolt by turning it in the counterclockwise direction with a 12mm socket and a 3/8" drive ratchet.

Hold in the release tab and pull the regulator plug off the front of the alternator.

Set the B+ output terminal cover aside in a safe place.

Gently pull the small black plastic tab on the retaining clip out towards the right (driver) side of the car.

Slide the black plastic wire harness retaining clip off the metal mounting bracket.

Loosen the nut on the B+ output terminal by turning it in the counterclockwise direction with the 10mm socket and a 1/4" drive ratchet.

Locate the larger 14mm "pivot" bolt on the bottom of the alternator.

The bottom 14mm bolt is marked with a red arrow in Picture # 27.

Once the bottom 14mm pivot bolt and the top 12mm adjustment lock bolt have been loosened, spin out the long 12mm tensioner bolt.

Carefully push on the alternator to pivot it back towards the rear of the car.

This will release the tension on the serpentine accessory belt.

If the serpentine belt comes off the other pulleys or you are replacing the belt, check out my 2009-2013 Toyota Corolla Serpentine Belt Replacement Guide for a belt routing diagram.

Remove the short 12mm adjuster lock bolt by spinning it out by hand in the counterclockwise direction.

Loosen the 12mm bolt on the rear of the tension adjustment bracket.

Swing the tension adjustment bracket up and away from the alternator.

Slightly tighten the rear 12mm bolt on the tension adjustment bracket to keep it in the raised position and out of the way.

You might need to pivot the alternator back and forth a few times or wiggle it from side to side to loosen the mounting "ears" from the bracket on the engine.

Please be sure to use the Amazon Part Finder website to verify the correct replacement alternator for your vehicle since it may vary depending on the model year, trim level and whether it was built in North America or Japan.

The new or remanufactured alternator that you purchase probably won't be equipped with the small metal bracket for securing the wire harness in place.

Remove the bracket by turning the 10mm bolt in the counterclockwise direction.

Install the bracket on to the new alternator by tightening the bolt in the clockwise direction until it is snug.

The black plastic thermostat housing is held in place by two 10mm nuts.

Warning - If you remove the thermostat housing, the coolant will leak out.

Check out my 2009-2013 Toyota Corolla Coolant Change Guide for more information.

Line up the mounting brackets or "ears" on the bottom of the alternator with the mount on the engine.

Push the alternator into place over the mounting point on the engine.

Make sure the bolt holes in the mounting ears on the alternator are lined up with the bolt hole in the bracket on the engine.

I chose to place a small amount of Loctite Blue (medium strength - removable with hand tools) to all of the bolts on the alternator to help prevent them from possibly vibrating loose.

Loosen the bolt on the rear of the tensioner bracket.

Lower the tensioner bracket down towards the top of the new alternator.

Slightly tighten the large 14mm bolt.

Do not tighten the bolt all the way since you still need to adjust the belt tension.

Lower the serpentine belt over the alternator pulley.

Spin in the front long 12mm tensioner bolt in the clockwise direction.

Check the tension on the serpentine belt by grabbing it at the middle of the longest run from the alternator down to the crankshaft.

Try twisting the belt until it is about 90 degrees (perpendicular) to the other section of the belt laying flat on the pulleys.

If you can easily twist the belt past 90 degrees, the belt is too loose.

If you can barely twist the belt and there is no way you can reach 90 degrees, the belt is too tight.

The tension is correct when you can just barely twist the belt to 90 degrees (perpendicular) to the rest of the belt.

Another method for checking the tension is to hold a ruler against the longest run of the belt and pull the belt down away from the ruler.

The correct tension setting is when the belt can only be pulled about 1/2" (0.50 inch) or about 13mm away from the ruler.

Once you are satisfied with the belt tension, tighten the 14mm pivot bolt at the bottom of the alternator.

If you have a torque wrench, the service manual specification for the 14mm pivot bolt is 32 lb-ft of torque.

Make sure that the rear 12mm bolt on the tensioner bracket is tightened to 14 lb-ft of torque as well.

Push the wire harness plastic retainer over the metal bracket on the front of the alternator.

The retaining clip should "click" securely into place. Double check that the harness can not be pulled off the metal bracket.

Push the ring terminal at the end of the B+ output cable to the mounting post on the front of the alternator.

Spin on the 10mm nut and tighten it in the clockwise direction with the 10mm socket and a 1/4" drive ratchet until it snug.

You should hear or feel the connector "click" securely into place.

Double check that all of the bolts and electrical connections are securely in place.

Carefully push the negative terminal on to the "-" battery post.

Tighten the terminal nut in the clockwise direction with the 10mm socket and a 1/4" drive ratchet until it is snug.

Try to avoid over tightening the terminal nut to prevent from cracking the battery post which could lead to an acid leak.

Start the engine and listen closely for any strange noises.

If you do hear any strange sounds, immediately turn off the ignition and double check your work.

The best way to test your new alternator is with a digital multimeter tool.

If your 12V battery is fully charged it should have a voltage of about 12.60V or higher with the engine turned off. My brand new Interstate battery had a reading of 12.73 volts.

Start the engine and carefully check the voltage on the battery terminals again.

If the new alternator is working properly, the voltage should have a reading of at least over 13 volts to just over 14 volts.

If the alternator is outputting 15 volts or higher, there might be a problem with the voltage regulator.

My new alternator had a reading of 14.45 volts.

If you hear a "chirp, chirp, chirp" sound from the belt, it might be too loose.

If the engine has a rough idle, idles at a lower RPM or you hear a loud screeching sound when you start the engine, the belt is probably too tight and should be loosened.

To adjust the tension, loosen the lower 14mm bolt and loosen the 12mm tension adjustment lock bolt.

Then either turn the long 12mm tensioner bolt in the clockwise direction to tighten the belt or in the counterclockwise direction to loosen the belt.

Be sure to write down the procedure in your vehicle's service records.

Please check out my other Corolla DIY tutorials at the links below -

2009-2013 Toyota Corolla Repair & Maintenance Guides

2014-2018 Toyota Corolla Repair & Maintenance Guides

2003-2008 Toyota Corolla Repair & Maintenance Guides