How to Replace an Alternator on an Cars

by Contributing Writer; Updated June 12, 2017

The power-train control module (PCM) on certain years and models of the Mercury car controls the charging system by determining the best voltage (the optimal voltage set point) and sending the information to the voltage regulator. There are three pins on the voltage regulator. They're usually internal, within the alternator. One of these is the generator communication line, which communicates the set point from the PCM to the voltage regulator. The second pin is the generator monitor. This pin communicates load and error information from the alternator to the PCM. The third pin on the voltage regulator is the A-circuit pin, which senses battery voltage and sends this information to the PCM.

Under The Hood:

 How to Replace an Alternator on an Isuzu Rodeo

Alternator Replacement for Isuzu Rodeo

Remove the small skid plate with a 14 mm socket. Remove the ground wire from your battery so the alternator does not have power.

Loosen the six 19 mm lug nuts on the passenger side tire. Do not remove them yet. Apply the parking brake and use the floor jack to lift the front passenger side of the vehicle. Insert a jack stand and support the vehicle on the frame railing behind the passenger side tire. Once the vehicle is supported by the jack stand, remove the tire.

Loosen the 14 mm bolt on top of the alternator and then the 12 mm bolt that goes through the adjuster arm. There might also be a 10 mm adjuster bolt that needs to be loosened as well. Slide the belt off the alternator by lifting up. Do not remove any of these bolts yet.

Remove the plastic wheel well apron that covers up the engine bay from the underside of the vehicle. Pop out the eight fasteners with a flathead screwdriver. This will create the space to remove the alternator.

Remove the 14 mm bolt that was loosened in Step 3. Then remove the 12 mm bolt. The alternator can now be positioned through the engine bay so that it can be pulled out of the wheel well.

Disconnect the electrical connections on the alternator and remember or mark where they were installed. One of the connections will be secured with a 10 mm nut. Use an open-ended wrench to undo the nut and pull out the old alternator. Hold the new alternator in the same spot so that the electrical connectors can be reinstalled. Tighten the 10 mm nut and then reconnect all the electrical connectors.

Slide the alternator up through the wheel well and into position in the engine compartment. Reattach the 14 mm bolt onto the top of the new alternator and the 12 mm bolt through the alternator and into the adjuster arm. Adjust the tension as necessary.

Items you will need

  • Floor jack

  • Jack stands

  • Ratchet

  • 10 mm, 12 mm, 14 mm and 19 mm sockets

  • Flathead screwdriver

 How to Replace the Alternator in a Jeep Wrangler

Disconnect the negative battery terminal from the battery by using a hand wrench to loosen the connection clamp.

You next have to remove the drive belt from the alternator pulley. Locate the serpentine belt tensioner and use the serpentine belt tool to relieve tension on the belt. Turn the tensioner clockwise until there is enough slack in the belt to slide the belt off of the alternator pulley. Do not remove the belt completely unless you're replacing it. Some older Jeeps may have an alternator pivot bolt to loosen and then pivot the alternator on the bracket to relieve tension on the belt.

Remove the two alternator mounting bolts using a ratchet wrench.

Unsnap the B+ terminal cover if equipped on the back of the alternator. Remove the B+ terminal retaining nut with the ratchet and a socket. and remove the terminal from the alternator.

Unplug the other wires from the alternator, making careful note of where and how they connect. It may be useful to take a picture with your digital camera, or sketch out the wiring diagram, before removing the wires.

Pry the alternator out of the alternator bracket with a screwdriver.

Position the new alternator onto the alternator bracket and reverse the procedure to reinstall.

Items you will need

  • Serpentine belt tool with adapters Hand wrench set Ratchet and socket set Screwdriver Replacement alternator

 How to Replace the Alternator in an Acura

Open the hood on the Acura model vehicle and lock the hood in place.

Remove both of the battery cables from the battery with the 1/2-inch drive ratchet and a small socket.

Pull the battery out of the engine compartment and place it on a table or any place that is off the ground. Then, pull the battery tray out of the engine compartment and place it on the ground.

Remove the lower alternator mounting bolt with the ratchet and a socket. Then, remove the adjustment bracket locking nut and the adjustment bolt with the ratchet and socket.

Slide the pry bar under the alternator and pry the alternator toward the engine. Then, reach down and pull the alternator belt off the alternator pulley.

Pull the alternator up out of the bracket and position the alternator inside of the bracket so that the wires on the back of the alternator can be accessed.

Unplug the wiring harness plug by pushing in on the locking clips and pulling out on the plug at the same time.

Remove the nut from the red wire connector with the ratchet and a socket. Pull the red wire off the back of the alternator.

Remove the nut from the black wire connector with the ratchet and a socket. Pull the black wire off the back of the alternator. Then, pull the alternator out of the bracket and place it on the ground.

Position the new alternator into the bracket. Reinstall all of the electrical components back onto the rear of the alternator.

Rotate the alternator so that the mounting bolt and the adjustment bolt will line up with the mounting bracket. Reach down and pull the belt back over the alternator pulley.

Screw the lower mounting bolt back into the bottom of the alternator. Then, reattach the adjustment bolt and the locking nut on the front of the alternator. Tighten the adjustment bolt down tight with the ratchet and socket until the belt is tight. The belt should have no more than one half-inch of slack in it. Then, tighten the lower mounting bolt and the lock nut down tight with the ratchet and socket.

Place the battery tray back into the engine compartment. Set the battery down into the battery tray. Reinstall both battery cables back onto the battery and tighten down tight with the ratchet and socket.

Crank the Acura and let the engine run for about one minute so that the new alternator can completely charge the battery and the electrical system. Turn the engine off and close the hood.

Items you will need

  • 1/2-inch drive ratchet

  • 1/2-inch drive socket set

  • Pry bar

  • Replacement alternator

 Replacing the Alternator on a Lexus LS400

Disconnect the negative battery terminal. Use a wrench to loosen the nut.

Loosen the alternator pivot bolt with a socket and ratchet and push the alternator toward the engine slightly to loosen the belt. Pull the belt off the engine. Unplug the wiring harness from the alternator and remove the ground wire using a wrench to remove the nut.

Remove the bolts from the alternator using the socket and ratchet. There is the pivot bolt, and then a bolt at the bottom of the unit. Pull the alternator out of the car.

Put the new alternator in the car and loosely install the pivot and the bottom bolts. Put the alternator belt back on the car and pull the alternator toward the front of the car to pull the belt tight. Tighten the pivot bolt first, and then the bottom bolt with the socket and ratchet. Reconnect the negative battery terminal.

Items you will need

  • Metric socket set

  • Metric wrench set

 How to Change an Alternator in a 2001 Buick Century

Locate the negative battery terminal, then remove the retaining bolt holding the negative battery cable in place, using a wrench. Remove the cable from the battery and set it aside.

Move to the passenger-side fender so you are facing the front of the engine. Locate the serpentine belt tensioner on the engine and place a socket and breaker bar on the bolt in the center of the pulley. Rotate the tensioner counterclockwise to relieve the tension on the belt, then slide the belt off the alternator pulley.

Locate the wiring harness connector on the back of the alternator. Depress the locking tab on the connector and pull it free from the alternator. Lay it aside, then find the battery connection on the back of the alternator. Remove the locking nut from the terminal with a wrench and pull the wire off the terminal.

Locate the retaining bolt on the top of the alternator and remove it with a socket and ratchet. Find the second bolt at the bottom of the alternator, on the front of the unit. Remove it with a socket and ratchet, then lift the alternator off the engine and out of the engine compartment.

Set a new alternator in place on the engine and install the upper and lower retaining bolts. Torque the bolts to 37 ft-lbs. with a torque wrench and socket.

Plug the wiring harness connector into the back of the new alternator, making sure it locks in place. Slide the battery output wire onto the BAT terminal, followed by the retaining nut. Torque the retaining nut to 15 ft-lbs. with a torque wrench and socket.

Rotate the serpentine belt tensioner counterclockwise, then slide the belt onto the new alternator. Rotate the tensioner back to the home position and remove the breaker bar and socket from the assembly.

Install the negative battery cable end onto the negative battery terminal. Install the retaining bolt and tighten it with a wrench.

Items you will need

  • Wrench set

  • Breaker bar

  • Socket set

  • Ratchet

  • Torque wrench

 How to Change the Alternator of a 2001 Oldsmobile Aurora

Disconnect the battery by turning the positive terminal bolt counterclockwise and pulling the terminal free of the post. Set the terminal aside, away from the post.

Remove the radiator to gain access to the alternator by taking out the fan shroud, fan and radiator assembly. The fan can be unplugged from the wiring harness by pulling the adapter plug out of the socket, then the fan shroud and fan can be removed in one piece by turning the four corner bolts on the shroud counterclockwise. Lift the fan and fan shroud up and out of the engine compartment. Disconnect the coolant hoses by turning the hose clamp screws counterclockwise and working the hoses off. Collect any spilled coolant in a drain pan. Turn the top radiator mount bolts counterclockwise and the entire unit can be lifted directly up, out of the engine.

Remove the power steering pump lines by turning the line bolts counterclockwise. Removing the lines can give enough access, but the entire pump can be removed if required. Turn the mount bolts counterclockwise and the pump can be taken out.

Remove the belt from the alternator by pressing firmly on the tension pulley arm, then sliding the belt out from under the idle pulley wheel. Release the arm and unwrap the belt from the alternator. It is not necessary to completely remove the belt from the engine.

Disconnect the wiring harness from the alternator by pulling the adapter plug from the alternator's socket. Turn all of the mount nuts counterclockwise, while holding the opposing bolt head with a socket. Slide the bolts out, and the alternator can be manipulated out of the car. Replace the alternator with a new unit, and reverse the procedure to install. Refill the cooling system with the proper level of coolant once the cooling system is reassembled. Reconnect the battery and start the Aurora.

Items you will need

  • Socket set

  • Screwdriver

  • Pliers

  • Wrenches

 How to Replace an Alternator on a Mercury Sable

Remove the battery ground cable and secure it away from the battery's negative terminal. Jack up the right side of the Sable with the floor jack and support the Sable on the jack stand. Remove the right front wheel using the lug wrench. Remove the right fender splash shield using the appropriate sockets.

Loosen the tension on the accessory drive belt, using the appropriate socket to push the tensioner away from the belt. Lift the belt off the pulleys. Remove the crankshaft pulley using the appropriate socket. In most cases, you turn the pulley bolt to the right to tighten it and to the left to loosen it. The Sable's crankshaft pulley bolt is a left-handed bolt. Turn it clockwise (to the right) to loosen it.

Unplug the alternator's harness connectors. Unbolt the alternator mounting bolts and remove the alternator.

Install the new alternator, tightening the mounting bolts to 18 foot-pounds of torque. Reinstall the crankshaft pulley, keeping in mind that you must turn the bolt counterclockwise (to the left) to tighten it. Plug the harness connectors into the alternator. Tighten the crankshaft pulley bolt to 74 foot-pounds of torque.

Reinstall the accessory drive belt, following the routing diagram located on the fan shroud or the underside of the hood. Reinstall the right fender splash shield using the appropriate socket. Slide the wheel onto the studs. Tighten the lug nuts hand tight. Raise the Sable high enough to remove the jack stand, then lower the Sable to the ground. Tighten the lugs using the lug nut wrench. Reconnect the negative battery cable.

Items you will need

  • Set of wrenches

  • Floor jack

  • Jack stands

  • Lug wrench

  • Set of sockets

  • Torque wrench

 How to Replace an Alternator in an Isuzu Trooper

Disconnect the negative terminal on the battery with a wrench. Remove the air pump bolts and air pump to gain access to the alternator. Use a 3/8-inch drive ratchet and a socket to remove the air pump.

Loosen the lower adjuster bolt in the alternator. Swing the alternator toward the engine, then remove the belt. Remove the large diameter, 10-gauge wire on the back of the alternator, which is the battery wire. Use a wrench to remove the nut securing this wire. Pull the plastic electrical connector from the back of the alternator.

Remove the upper and lower bolts in the alternator, using the 3/8-inch drive socket. Remove the alternator. Install the new alternator and parts in reverse order of removal.

Items you will need

  • Set of wrenches

  • 3/8-inch drive ratchets

  • Set of 3/8-inch drive sockets

 How to Replace the Alternator in a 2000 Jeep Cherokee

Remove the cable from the negative battery terminal with a wrench.

Disconnect the two electrical connectors from the alternator.

Remove the alternator pivot bolt with a socket and ratchet.

Loosen the alternator adjustment bolt with the socket and ratchet but do not remove it.

Remove the drive belt once the bolts have been removed and the alternator has been lowered, putting slack in the drive belt.

Remove the alternator after removing the alternator adjustment bolt with the socket and ratchet.

Install the new alternator. Install the alternator pivot bolt and install the alternator adjustment bolt with the socket and ratchet but do not tighten the bolts, leaving enough movement in the alternator to install the drive belt over the alternator pulley.

Adjust the drive belt by placing a pry bar under the alternator to remove the slack in the belt. Instruct an assistant to tighten the alternator adjustment bolt and alternator bolt with a socket and ratchet while you pry up on the alternator.

Reconnect the negative battery cable to the battery terminal with the wrench.

Items you will need

  • Pry bar

  • Socket set

  • Ratchet

 How to Replace the Alternator in a Mercedes Benz

Examine the drive belt configuration. The Mercedes Benz line of vehicles uses a serpentine belt (one long belt) to power the alternator and a series of other electrical components. Note the orientation of the belt. There is a belt diagram on the underside of the hood and on the frame of the Benz next to the hood latch (on some models).

Release tension on the alternator belt. Turn the center tension pulley clockwise with a socket wrench. This will create slack in the belt.

Slide the belt off the alternator. You will need to remove the belt from all of the other components on the system as well.

Remove the electrical connector on the back of the alternator.

Remove the top and bottom alternator mounting bolts and slide the alternator out of the engine bay.

Install the new alternator. Installation is the reverse of the removal process. When installing the belt, it is best to use a new one. They're relatively inexpensive for the Benz and by the time an alternator needs to be replaced, the belt is usually worn to the point where it will likely need to be replaced soon as well. Make sure that the belt sits directly in the center of the pulley, and that the teeth on the belt sit in the pulley's grooves. Route the belt according to the belt path on the underside of the hood.

Items you will need

  • Socket wrench

  • Socket set

  • New alternator

  • Torque wrench

 How to Change an Alternator in a GMC Sonoma

Open the Sonoma's hood and locate the battery. Remove the negative battery cable from the battery with an adjustable wrench. The negative battery cable will be attached to the negative battery post, which has a minus (-) symbol embossed near or on the post. Secure the negative battery cable to the side so that it does not touch metal and cannot inadvertently slide into contact with the battery post.

Locate the alternator and the serpentine belt tensioner on the front of the engine. The alternator on the GMC Sonoma is located on the passenger side. Relieve the tension on the belt tensioner with a ratchet and a 13mm socket. Turn the tensioner counterclockwise and remove the belt from the alternator pulley only.

Remove the 13mm nut on the backside of the alternator. This nut is holding the wire connector to the rear of the alternator. Then pull the wire off the stud and lay it out of the way. Then pull the electrical plug out of the back of the alternator and lay it out of the way.

Remove the two main bolts holding the alternator to the alternator bracket. One bolt is through the top left-hand side of the alternator and the other bolt is through the bottom of the alternator in the center. Remove these bolts with a 13mm socket and ratchet. Turn the bolts counterclockwise to loosen and remove them from the alternator. Then slide the alternator out of the alternator bracket. Set the alternator aside.

Slide the new alternator into the bracket and slide the lower bolt in first. Then slide the top left-hand-side bolt in. Tighten the bolts down to the proper bolt torque settings. The proper torque settings for the alternator bolts on the GMC Sonoma series is 32 foot-pounds as recommended by the Haynes Repair Manual. You can use a torque wrench and a socket to get the proper torque settings. Once the alternator bolts are tight, plug the wire connector back in to the lower plug socket on the rear of the alternator. Also reattach the wire connector to the center stud and screw the 13mm nut back down tight over the wire connector.

Relieve the tension on the belt tensioner and slide the serpentine belt back over the alternator pulley. Release the belt tensioner and let it pull the slack out of the belt and bring the belt back to the proper tension.

Reconnect the negative battery cable to the battery post and tighten the cable bolt back down tight with the adjustable wrench.

Crank the Sonoma and let the new alternator charge the battery. Make sure the serpentine belt is running evenly and securely inside the alternator pulley. Turn the engine off after 20 to 30 minutes and close the hood.

Items you will need

  • Adjustable wrench

  • Ratchet

  • Sockets

  • Small torque wrench

  • New alternator

 How to Replace an Alternator in a Volvo 240

Alternator Removal

Working on a cold engine, disconnect the negative battery cable, then disconnect the electrical leads to the alternator.

Loosen the alternator adjusting bolts and position the alternator so that the drive belt may be removed.

Take out the alternator adjusting bolts and mounting bolts. Remove the alternator.

Alternator Replacement

Reverse the removal steps above by first positioning the new alternator in place.

Reinstall the mounting and adjusting bolts, but do not tighten completely.

Replace the drive belt, making sure to adjust the tension correctly. You should be able to depress the drive belt 5 to10 mm midway between the pulleys. Once the tension is correct, tighten the bolts.

Reconnect the electrical leads to the alternator.

Reconnect the negative cable to the battery.

Items you will need

  • Socket wrench set

  • Torque wrench

  • Replacement alternator

 How to Replace the Alternator in a GMC Safari Van

Disconnect the negative cable from the battery terminal. The cable has a retaining nut and clamp that you must loosen. Use the socket wrench to loosen the retaining nut on the clamp over the battery terminal and pull the clamp off the negative terminal.

Open the hood of your Safari and locate the fan cowling. This is a cover for the van's cooling fan.

Loosen and remove the several screw bolts holding the cowling in place using either a screwdriver or the socket wrench (either one will work for these bolts).

Remove the cowling and set it aside.

Unplug both of the electrical connections on the alternator. One of them is readily visible from the front but there is one hiding behind the alternator that you may not be able to see very easily.

Loosen the tension on the alternator belt using the breaker bar and the socket wrench. Place the socket wrench on the belt tensioner located on the pulley next to the alternator pulley. Then, place the breaker bar over the end of the socket wrench to give you enough leverage to loosen the tension. The tensioner can only be adjusted one way to loosen tension on the pulley enough for you to remove the belt.

Remove the alternator belt.

Unbolt the top and bottom bolts on the alternator and remove them.

Remove the alternator. It should pull straight up out of the engine bay. Install the new alternator. Installation is the reverse of removal.

Items you will need

  • Socket wrench and socket set Screwdrivers Breaker bar