The air conditioner compressor is the main component of any vehicle occupant
cooling and comfort control system. This component is basically a refrigerant
pump driven by the engine via a serpentine belt or on electric and hybrid
vehicles a small electric motor mounted inside the unit.
Responsible for receiving spent (low pressure) R134a refrigerant and
compressing it into the high pressure gas these units are prone to failure
which usually happens in one of two ways, either they can leak refrigerant or
they will suffer a mechanical failure, either way they must be repaired. Though
this job might be intimidating for some, the repair in the video is one of the most
difficult in the industry which I performed myself. Though appearances may differ, the process similar
for most vehicles.
In the guide below I will discuss this procedure in detail while giving you
tips and information the video below may have missed. Enjoy the show and
then travel through the information below to gain additional knowledge.
This job is typically done in under three hours but can save you hundreds of
dollars with the satisfaction you did the it yourself, so lets get started!
Tools and Supplies Needed
Air Conditioner Compressor
Air conditioner gauge set
AC vacuum pump
R134a refrigerant supply
If any of these items are needed they can be purchased at Amazon or a local
auto parts store.
Before work begins, park the vehicle on a flat surface, with the emergency brake
on, engine off, using a basic set of tools while wearing protective eyewear and
Air conditioner systems are filled with refrigerant under pressure, we must
check to see if any refrigerant is left in the system before disassembly this is
done using an a/c gauge set. If the system is "flat" and all the refrigerant has escaped, continue with
this guide. If the system is still has refrigerant present it must be discharged
before disassembly. Checking the pressure or refrigerant level is done through
the low side service port.
low side pressure port is located on the larger of the two refrigerant tubes. To locate this port follow the larger of the two refrigerant lines which connect
from the evaporator core (from firewall) to the rear of the compressor. Remove
the low side port cap and attach the gauge set connector valve to check system
Once the refrigerant has been removed, loosen the negative cable from the
battery terminal to disconnect, this will avoid accidental short circuits while
the work is being done. (Note: If the radio is being used, record
it's presets as they will need to be re-entered after the battery is
Unbolt and remove any tubing or hoses
to gain access to the serpentine belt for removal. This tubing is used for
emissions and air filter intake proposes and is usually easily removed by
undoing minor bolts or screws.
The serpentine belt must be removed which drives the compressor except for
hybrid and electric cars. Using a wrench or socket, release tension on the belt
by applying opposing force on the tensioner, this will loosen the belts grip on
the pulleys so it can be removed. once the belt is off it's a good time to
inspect and replace it if worn, glazed or cracked. This operation is easier on
rear wheel drive engine configurations than front wheel drive vehicles.
While some compressors are in plain sight others can be buried beneath a
layer of brackets and accessories such as an alternator or power steering pump.
To gain access remove additional
accessories such as an alternator which can be done by loosening and removing
wiring connectors and mounting bolts.
Once these obstructing accessories have been removed, locate the electrical
connector located on the front or rear of the compressor. This connector is uses
to energize the engagement coil if it's located in the front, or the internal
control valve if located in the rear. Use a small pick or screwdriver to release
the electrical connector. If this connector cannot be seen or its too difficult to
remove you can do so once the mounting bolts have been removed.
Once the refrigerant has been released
or recovered and the low side gauge pressure reading is at zero, locate and remove high
and low side refrigerant line mounting bolts or flare nuts depending on
manufacturer design. Again on some models this step may need to be performed
after the mounting bolts have been removed and the unit is loose.
After the bolts have been removed, firmly grasp and wiggle the line bulkhead
of each refrigerant line to slowly pull
upward and disconnect. There is an
O ring seal which can make a tight fit and small amount of refrigerant (pressure)
maybe released as well, complete this step by removing both tube fittings.
Once all wiring harness connectors and refrigerant lines have been removed,
locate and remove lower and upper mounting bolts. These bolts can consist of
long and short bolts which sometime can be obscure and difficult to get to, if
so, use a universal joint socket or small wrench to aid in the removal. Always
leave at least one bolt connected to the bracket or block but loose, to
hold the unit in place.
Next, grasp the unit while removing the last mounting bolt, the compressor is
heavy and a little bit awkward to hold so be careful it doesn't fall and cause
damage to the unit or yourself, once completely loose remove it from the engine bay.
This can take some work and sometimes you must move the engine a tiny bit in it's
mounts or possibly even loosen the engine mounts and use a jack under the oil
pan to help lift it slightly. Other times a radiator or cooling fan shroud must
be removed as well.
Once the unit has been removed,
turn the pulley or clutch to determine it's condition by checking for rough
movement or grinding noises, if present this sometimes means the system is contaminated with
foreign metal debris from the failed unit which can plug the
orifice tube or expansion valve. In these cases the system must be flushed by using an a/c
system flush kit which can be purchase from Amazon or the local parts store.
If the system is completely plugged its best to replace the expansion valve
or orifice tube along with the receiver dryer or accumulator depending on the
system design. Inspect for obvious contamination by looking inside the
refrigerant lines or intake and exhaust ports for metal particles.
Compare the new compressor to the old unit to ensure a proper installation.
Sometimes the replacement unit can look slightly different due to updates and
slight design variations, the one thing to look for is the configuration of the
refrigerant ports on both the intake and exhaust sides. Also, check the belt pulley by
counting the number of ribs which the belt must ride on, also the outside diameter must be correct.
When installing the new compressor into the engine bay it's a good idea to transfer the mounting bolts
from the old unit or before lower it in, this will help for
Though the system has peg oil throughout
it's internal workings which is usually including in the compressor, it's a good idea to add a slight
amount (1/2 ounce) of compressor oil to ensure proper lubrication before installation,
then reinstall dust caps. Some units have oil already installed, read the installation
instructions for more information which are supplied with the unit.
O rings are used to seal the high and
low side lines to the compressor housing, these sealing surfaces must be clean and
free from dirt or damage to help them hold the refrigerant. Use a small screwdriver or pick
to carefully remove the old O ring seals from both the high and low side lines
without scoring the sealing surface where the O ring sits, this will ensure a
Match the old O rings to the new ones
to ensure a proper seal, keep an eye on the thickness because some O rings can
be smaller in diameter then others. It's a good idea not to reuse the old seal
because they become flattened over time due to pressure and heat and may leak
which would cause the job to be redone which means vacuuming down and recharging
After cleaning the fitting thoroughly, install a new O ring seal on each the
low and high side fittings, once installed apply a thin layer of peg oil over
the O ring to help the installation without damaging or cutting the new seal, repeat this process
for each line.
Clear any hoses or lines while gently lowering the new unit into the engine
bay, hand thread in the mounting bolts which will hold the unit into
it's mounts or engine block.
Once all mounting bolts have been hand
threaded in, use a wrench or socket to tighten the mounting bolts evenly in a
cross pattern, this will help to not distort the housing which can cause
Remove the port dust covers and install
both high and low side refrigerant lines with the mounting bolts and then tighten,
these bolts don't need to be extremely tight just snug enough to not come loose
and seal against the housing.
Once all mounting bolts are tight, make sure the electrical connector is
clean before reconnecting it to the engagement coil or refrigerant control
Reinstall any accessories such as the
alternator by gently lowering the unit into the engine bay while installing the
mounting bolts and electrical connectors.
While holding back the serpentine belt
tensioner, reinstall the belt back into place, once completed double check the
alignment of the belt by inspecting the pulleys of each accessory and drive
pulley located on the engine crankshaft, make sure all belt pulleys are properly
seated against the belt.
Once completed reinstall any tubes or hoses removed in the replacement
process, continue by tightening all bolts, screws, clips or brackets previously
removed. Now the system is ready to be
vacuumed down and recharged, never simply
fill the system with refrigerant because moisture is present inside the system
due to the normal atmosphere once it was opened and will cause
the compressor to fail prematurely. Using an a/c gauge set and vacuum pump
proceed in this operation of moisture removal and system recharge.
Air Conditioner Troubleshooting
An air conditioner compressor can fail either by leakage or by an internal
mechanical problem which is usually accompanied by abnormal noises while in
operation. High mileage car's trucks and SUV's are prone to failure due to
usage. If the vehicle is used in colder weather and the system is not used much
it's a good idea to turn the system on occasionally to help move the oil around
the system which will help lubricate the seals and help the compressor last
Need more information about this repair? Please visit our forum where
air conditioner compressor questions have been answered by our mechanics.