The AC compressor should last for the entire life of the car,usually 8-10 years.
System maintenance and compressor efficiency
The compressor’s efficiency can be improved by maintaining the correct working conditions. This involves keeping the suction pressure as high as practical and the head pressure as low as practical within the design parameters. A dirty evaporator will cause the suction pressure to drop. When the suction pressure goes below normal, the vapor that compressor is pumping become less dense and gets thin (sometimes called rarified vapor).The compressor performance declines. Low suction pressures also cause the high-pressure gases caught in the clearance volume of the compressor to expand more during the piston’s downstroke.This gives the compressor a lower volumetric efficiency. These gases have to expand to a pressure just below the suction pressure before the suction valve will open. Because more of the downward stroke is used for reexpansion, less of the stroke can be used for suction. Suction ends when the piston reaches bottom dead center. Low evaporator pressures cause high compression ratios.
Dirty condensers also cause compression ratios to rise, but they do not rise as fast as with dirty evaporator.A dirty condenser makes the head pressure to rise. This causes the amount of refrigerant in the clearance volume (at the top of the compressor cylinder) to be greater than the design conditions allow and the compressor efficiency to drop.
If there is a dirty condenser (high head pressure) and a dirty evaporator (low suction pressure), the compressor will run longer to keep the refrigerated space at the design temperature. The overall efficiency drops.
Evaporator core and condenser core maintenance will increase the life of the air conditioning compressor,improve the A/C efficiency and cooling capacity.With regular A/C maintenance we are saving money in the long run and getting the most out of the air conditioning system.
A bad compressor could affect the engine in your car. If your compressor’s pulley bearing goes bad, your engine can stall due to the stuck compressor or the serpentine belt may break affecting all the accessories moved by the serpentine belt.
Clutchless variable displacement piston compressors and compressor lock up.
Clutchless variable displacement compressors have extra protection in case the compressor seizes.In the event a compressor failure occurs the bridges on the clutch assembly will break and only the pulley will keep running, allowing the engine to keep running.
For an ac compressor repair we need not only to repair the symptom,
but the cause too.
The a/c compressor is considered the heart of the air
conditioning system. It is a pump that can be driven by a serpentine or V belt,
an electric motor or in some cases both. There are 3 common compressor designs
in use today, they are:
piston type compressor.
Rotary vane type compressor.
Scroll type compressor.
The ac compressor should last for the entire life of the vehicle.
The automotive ac compressor could fail because of age, a design or
construction defect during manufacturing or because something in the air
conditioning system is not working properly and is putting excessive stress on
Before replacing or servicing any ac compressor we should
investigate what was the cause of the failure, because the chances of damaging
the new compressor are pretty high if we don’t correct the cause.
properly diagnose a faulty a/c compressor clutch coil in your car?
If a voltage of 12 DC volts or greater is present on the clutch
coil but the clutch isn’t engaging it doesn’t necessarily mean that the clutch
coil is bad. A compressor clutch can also fail from mechanical problems, such
as an excessive air gap between the pressure plate and rotor, or oil on either
of these components. A/C compressor clutch failures are usually a symptom of
another problem in the air conditioning system. If the problem isn’t diagnosed
and repaired, another ac compressor clutch failure will occur.
Some common problems
automotive a/c compressors may experience.
1-High head pressures, due to:
1.1-Overcharged ac systems.
1.2-Condenser fan not working at all or working not efficiently enough.
1.3-Clogged up with road debris, condenser core.
1.4-Contaminated a/c systems, with non-condensable gases.
2-Frequent clutch cycling due to:
2.1-Low refrigerant charge.
2.2-Faulty cycling switch.
3-Lack of lubrication or incorrect type and oil viscosity.
4-High resistance in clutch ground circuit.
5-Compressor bearing contaminated with other engine fluids (coolant,power
What is the cause of an ac compressor clutch not engaging?
The cause of an ac compressor clutch not engaging could be:
1-Electric or electronic fault of any
of the compressor control devices or ac compressor circuit protection device.
2-Faulty or wrong signal input to the
BCM or PCM.
3-Faulty PCM or BCM not sending the
output signal to the compressor control device(ac compressor relay).
4-A/C compressor clutch excessive air
5-A/C system too low on refrigerant
charge due leakage in the air conditioning system.
6-Compressor clutch coil winding open.
7-A/C head control set switch damage or entire a/c control set damaged.
A defective clutch may be replaced; however, the cause of the failure should
be investigated to avoid a repeat failure.It may be less risky and more cost
effective to replace the complete compressor if the condition of the compressor
is suspected due to age or mileage.
On variable displacement electronically or pressure controlled compressor,
the valve that controls the ac compressor crankcase pressure may be faulty and
the system will perform poorly or won’t cool at all.
How much does it
cost to fix an AC compressor?
The cost to repair an ac compressor will depend on the make, model and year
of the car. There is a really big difference in terms of time and cost between
replacement of the whole clutch assembly or the entire compressor.The labor only for an
ac compressor can range from $ 285.00 to $ 500.00.The price of the compressor
will depend on :
-The type of compressor.
-It could be piston type fixed displacement compressor
-Completely electric compressors for hybrid or electric vehicles.
The a/c compressor could be: a rebuilt or used compressor a new aftermarket
or OEM (Original Equipment Manufacturer).There will be differences in terms of
quality , warranty length and price according to which one of this options we
choose when buying an a/c compressor. The
ac compressor price range could be from $200.00 to $ 800.00.
What are the symptoms of a bad AC
1-No cold air from the vents.
2-Clicking sound from under the engine.(Compressor clutch
engaging and disengaging)
3-AC not working.
4-Noise under the engine with the a/c climate control on.
5-Burned rubber smell coming out from the engine compartment.
6-Looking at ac gauges set pressure; typical weak or damaged
ac compressor pressures are High side pressure too low and Low side pressure
an AC compressor be repaired?
The air compressor may be remanufactured or rebuilt. The
price range for labor only is $285.00 to
$500.00.This is an option many people choose ,because of the price difference
between a new compressor or a rebuilt one. It may seem you are saving some
money, but we think that in the long run buying a new compressor is always the
Can I drive my car
with a bad AC compressor?
The AC compressor pulley is a free spinning
pulley that has a clutch on it. It is designed in such a way that during
catastrophic compressor failure and compressor crankshaft lock-up or damage the
pulley will be able to rotate freely on its internal bearing and the car could
be taken to a safe place for service.
A/C compressor complex control system.
Different inputs Volkswagen uses to reduce
compressor output or turn it off:
High pressure > 464 psi
< 3 volts
Low pressure <
Engine start <
Blower stage 0
temperature < 37.4 F
temperature > 244.4 F
unit kick down coolant fan.
Low or high vehicle battery voltage
Pressure sensor fault
RPM > 3000 > 5 sec
Vehicle speed <10 mph
Power consumption of compressor
How to add oil to a compressor?
Analysis of Denso A/C Compressor warranty claims shows that in a quarter of all cases the use of incorrect oils, such as universal oils or oil mixtures, inevitably leads to seizure and damage. This is because universal oils are PAO-oils or mineral oils with a different viscosity to that of synthetic PAG-oils. PAO-oils do not mix well with PAG-oils and with refrigerant R134a or R1234yf, leading to poor lubrication and increased wear. Installing the ac Compressor without balancing the oil in the system, gives a high risk of liquid lock, due to too much oil in the A/C system! When adding oil to the ac compressor in your car one out of two methods could be used and the right one will depend on the type of compressor. Oil could be added through the ac compressor oil service port or through the low side or intake of the compressor. Always add oil through the oil service port if it comes with one or compressor damage may result.