Got a battery warning light on? This most likely means the alternator has
gone out and needs to be replaced. This is a common problem for most vehicles
but it isn't as bad as it sounds because most assembly's can be replaced in
about an hour using everyday tools. You will be able to save a good chunk of
change by changing it yourself or at least know what you are paying for when
taking your vehicle into a garage for repair. If you are not sure about the
performance of the voltage output of the unit is will need to be tested.
See Also: How to Test an Alternator
By watching this video and reading the repair guide below you will gain
knowledge if you want to do it yourself or have a garage do the work for you,
though appearances may vary the procedure is the same for
most vehicles. Once you are done watching the video follow the guide below to
get tips and information you may have missed in the video.
You can get a high quality OEM factory such as AC Delco, Motorcraft or Nippon
replacement units and a serpentine belt from Amazon for about the same price the
repair shops can buy them for. Follow the step by step guide below and get
Tools and Supplies Needed
New serpentine belt
Basic tool set
Protective eye wear and gloves
Park your vehicle on level ground with the engine off with the emergency brake
on, use a basic set of tools while wearing eye protection and gloves. If needed,
raise the vehicle using a floor jack and secure with jack stands.
Loosen and remove the negative
battery cable, push the cable away from the terminal to avoid accidental
connections if the cable wants to wander back over to the terminal. This step is
to remove electrical power for the vehicle to avoid short circuits when working
with the wiring harness.
Record the radio presets if you want to re-enter them when the job is
complete. Avoid removing the positive cable end because it can ground out to the
body or accessory while using a wrench.
The serpentine belt will need to be removed, located the belt tensioner and hold
reverse tension against it using a wrench, socket or breaker bar. This will
allow the belt to be removed from the alternator pulley, once the belt has been
removed inspect it for cracks and glazing because now would be a good time to
replace it with a new one.
Remove the dust boot from the main power terminal to expose the main power
wire. If the wiring is difficult to access, you will be able to disconnect the
wiring once the alternator is loose from the engine. All alternators are
designed with a main power cable (large gauge) that is connected directly to the
battery for main charging purposes.
Using a socket or wrench remove the nut by turning it counterclockwise. After the nut has been removed, grasp
the main power cable and lift it from the alternator charge terminal.
Next, locate the wiring harness,
grasp the dust boot and pull it back enough to access the electrical connector.
While releasing the safety clip on the
side of the connector, gently pull to outward to remove the wiring harness.
These connectors can be stuck because of the weather pack seal which you might
need to wiggle to remove.
Clear any hoses or wiring by removing mounting bolts or screws, once
a wrench or socket to remove the upper mounting bolt and bracket.
Locate and remove the lower mounting
bolt. This bolt can be a little tight so keep a good grip on the wrench or
socket while placing the wrench or socket firmly on the head of the bolt.
After the mounting bolts have been removed, grasp the unit and move it back and forth
while pulling upward, this will help release the press
fit (lower mounting bracket) used to hold the alternator in place.
Once the old unit becomes loose in the engine bay, get a good grip in on it
to gently lift and remove it. This step can take some trial and error while
rotating the unit while some minor adjustments (loosen) to surrounding fan
shrouds or radiator hoses that may get in the way of the removal.
Once removed, check the old assembly to the replacement unit, including electrical plug,
mounting bolt locations and pulley size to ensure a proper installation. Also
count the grooves on each of the pulleys they should be the same.
Most lower mounting brackets include a press fit sleeve that must be forced
slightly outward to make room for the replacement unit, this step is important
because installing the new unit would be very difficult if not impossible
without this step.
Using a large punch gently or metal bar to hammer the sleeve outward. This can
take a little finesse but stay with it because it only needs to be moved a
little bit to get the lower bolt installed.
Here is a close up shot of what the job should look like when completed, now the
lower boss of the housing will slip onto position easily.
Gently lower the replacement unit into the engine bay while being carefully not
the damage any of the surrounding components such as the radiator. The radiator
core is made of thin aluminum and it can be easily damaged which would not make
your day if you cause a leak.
Once the replacement unit is in place reinstall
the lower mounting bolt, leave the bolt hand tight until the installation of the upper
bolt. If you tighten the lower bolt first the upper bolt might bind which can
cause the bolt to strip out.
Now hand thread in the upper mounting bolt
and tighten, then tighten the lower bolt as well. These bolts need to be snug
but don't over tighten which can cause the bolts to strip out especially the
upper mounting bolt because it's smaller is size.
After the mounting bolts are tightened,
reinstall the computer wiring harness that monitors the voltage output along
with the rubber weather boot, be sure the connector is free from dirt and
Reinstall the main charge cable and mounting
nut, gently tighten the cable into place and do not over tighten. This
electrical terminal this made of a hard plastic and is used as an insulator
which can break causing an internal short hindering the charging operation. Reinstall
the rubber weather boot to keep any moisture from entering the connection which
will cause corrosion and more problems further down the line.
If the wring harness has mounting clip reinstall them to keep the harness from
wearing through and touching ground which will blow the charging system fuse and
possibly damage the new unit.
Next, reinstall any hoses or brackets removed in the replacement process.
After checking the conditioner of the serpentine belt and replacing it if
needed, reinstall the belt. Do this by holding tension against the tensioner and
then release it once the belt has been routed and in place. If you are confused
by the routing of the belt which happens to the best of us, use a belt routing
diagram made for your vehicle.
After the belt installation is complete use a flashlight to check the position
of the belt on each one of the accessory pulleys to make sure all of the belt
ribs are correctly positioned.
Now you are ready to connect the battery negative cable back up gently touch the cable to
the battery post, there should be a small spark while installing the cable end
to the terminal then tighten the cable end. If a large spark is generated the
alternator charge cable has grounded and needs to be rechecked, do not reconnect
the battery cable until this problem has been fixed. It doesn't happen very
often but it's something you should know.
When the job has been completed start the engine and observe the battery
warning light which should be out. It's a good idea to check the new
alternator's voltage output using a voltmeter.
How it works
An alternator is designed to supply electrical power (13.6 to 14.6 volts) to
a vehicle when the engine is operating while charging the battery for future use.
A serpentine belt is used to deliver rotation from the engine via the main drive
A large power terminal is used as the main voltage feed to the electrical
system which is usually connected to the positive battery post or fuse box, most
units are designed with a built in voltage regulator which helps
stabilize the voltage output.
This main power feed is used to power circuits throughout the vehicle.
A wiring harness connector is used by the computer PCM to control and monitor
the voltage regulator during variable engine speeds (RPM's) and voltage demands.
The assembly works on the principle of electromagnetism, by turning the
magnetic armature inside a wire field which has been electrified to produce AC
(alternating current) voltage. A series of diodes (6) convert AC to DC voltage
which is needed for the electrical system. An armature is supported by two
roller bearings on either end of the housing, voltage is transferred to terminals at the rear of
the housing via a spring loaded brush set.
A common problem is undercharging, this condition is often accompanied
by symptoms such as a battery warning light, low state of battery charge, poor or erratic
performance from electrical components.
Unit will overheat due to extreme usage causing a failure.
Poor battery condition can cause failure.
Weak voltage can cause the battery to slowly drain.
Once jump started a severely discharged battery can cause failure and overload
the unit and fail internally, if this occurs replace or recharge the
A serpentine belt must be in good condition
Clean battery terminals regularly
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