Tag: ac compressor repair

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/C compressor locked up.European cars

Can I drive my car with a bad AC compressor?

Will a bad AC compressor affect the engine?

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.

Why does the compressor cycle on and off?

What causes a compressor to short cycle?

Low refrigerant charge causes rapid cycling.

Drive belts and blower resistors do not affect compressor cycling.An excessive air gap may prevent the clutch from engaging.

AC Compressor Repair.

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:

  1. Reciprocating piston type compressor.
  2. The Rotary vane type compressor.
  3. The 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 the compressor.

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.

How to 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 steering…etc) 

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 gap.

 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

-Pressure controlled variable displacement compressor

-Electronically controlled variable displacement compressor

-Scroll compressor

-Vane 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 compressor?

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 too high.

Can 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 best option.

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:

  1. High pressure > 464 psi
  2. Blower voltage < 3 volts
  3. Low pressure < 29 psi
  4. Engine start < 4 sec
  5. Econ mode
  6. Blower stage 0
  7. Outside temperature < 37.4 F
  8. Engine temperature > 244.4 F
  9. Engine control unit kick down coolant fan.
  10. Evaporator temperature
  11. Low or high vehicle battery voltage
  12. Faulty signal
  13. Pressure sensor fault
  14. RPM > 3000 > 5 sec
  15. Vehicle speed <10 mph
  16. Green mode
  17. 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.