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Compressors Maintenance Tips

Frig Air tips for the maintenance of the Compressors.

FrigAir and Sanden give you some suggestions for the maintenance of your compressors.

The core of the automotive A/C is the refrigerant circuit. Within this cycle, the heat from the cabin is exchanged with the ambient, transported by the refrigerant (e.g. R134a).  The components of a standard refrigerant cycle are the compressor, condenser, expansion valve, and evaporator. The compressor is the heart of the vehicles’ air conditioning system; it is a very delicate component, the principal source of disruption in the A/C structure.

The compressor is sucking in the refrigerant in a gas state with low pressure. After compressing it up to a higher pressure, the hot gas is pumped into the condenser. At this stage the refrigerant exchanges the heat with the ambient and cools down nearly to ambient temperature, the pressure is still high. At the Thermostatic expansion valve the refrigerant expands, pressure and temperatures go down. The cold refrigerant is now passing the evaporator and exchanging the heat with the hot cabin air.

The compressor is driven by a belt attached to the vehicle’s engine which is engaged by an electromagnetic clutch called the compressor clutch. The A/C compressor is activated by the electronic clutch. When the a/c is switched on a drum inside the belt pulley is magnetized attracting and locking the belt drive into place making it so that only when engaged does it add extra resistance.

In the A/C system, the performances of one component affect the performances of the rest, due to its delicate components when the A/C system fails, the first part that is suspicious is the compressor, and so it is the first part replaced. From Sanden’s experience: 30% of compressors replaced during the warranty period are without any problem; more than 65% are broken due to reasons not liable to the compressor, and less than 5% fail due to a compressor production defect. Wrong diagnosis and wrong repairs cause a high cost to all involved parties.

The main enemies of the compressor are hits, dirtiness, and bad refrigerant/oil circulation.


It is obvious that hits to the car can cause serious damages to the compressor. Hits can break the ears or the armature of the compressor and they can affect the right functioning of the pulley, causing noises and general wrong functioning of the compressor.


The refrigerant pumped from the compressor to the condenser must be without impurities, so it’s really important to have cleaned filters to prevent a lack of performance or damages to the system. Remember to flush the system after a compressor failure, because it could be contaminated with particles that can cause severe damage to the valves and subsequently to the right functioning of the compressor.


If we have conditions under which there is not a proper circulation of oil or refrigerant, the compressor internal parts will not be refrigerated or/and lubricated, and so the internal parts will be damaged.

The typical causes for wrong circulations of oil refrigerant are:

- Wrong amounts of oil/refrigerant. It is important to adjust the oil/refrigerant amounts to the one specified by the A.C. system manufacturer. In case of too small amounts of oil/refrigerant, the internal compressor parts will not be refrigerated/lubricated, and so the compressor will fail. The most difficult situation comes when a vehicle has had a crash and we do not know the amount of oil lost. In such cases, the best option is to do a flushing of the system and put the oil amount recommended by the A.C. system manufacturer.

- If any part of the system has a lock, the oil/refrigerant circulation will not be correct. Special attention must be given to the receiver drier, which has to be replaced after a compressor replacement, expansion valve proper functioning, and any other filters of the system as the one of the calibrated orifice.

- In the case of a small leak, the refrigerant amount will be decreasing in a slow way. It is thought that the compressor is protected from leaks by the pressure sensor. The pressure sensor protects the compressor in the case of a quick leak (Eg.: the condenser is broken in a crash), but it does not protect the compressors in case of a slow leak.

Recommended procedure

An expert mechanic must check all the symptoms before changing the compressor, so before proceed with the wrong procedures you need to make the right diagnosis, to help you with this process the compressor oil aspect is an excellent tool that can tell us what is happening with the compressor without disassembling it.

The clear yellow color is the aspect of oil in normal conditions.

The light grey color is common in compressors that have run for a short time (very new compressors) due to the surface treatment of compressor internal parts. Later on during the A.C. running the oil turns to normal color.

The green color indicates the presence of additives to detect leaks. As there are many additives in the market, Sanden cannot guarantee the behavior of the compressor when additives are added to the oil.

The orange color indicates the presence of humidity. The origin is due to poor vacuum, or components contaminated by water. A proper clean of the system and replacement of the received drier is required before proceeding to charge the A.C. system with refrigerant.

Dark grey indicates the presence of very small metal particles inside the oil. The origin is due to compressor wear/seizure as a consequence of wrong oil/refrigerant circulation.

The silver color indicates the presence of medium-size metal particles inside the oil. The origin is due to compressor internal damage, due to compressor defect or wrong working conditions, such as a liquid compression that creates abnormal efforts. The compressor must be replaced. A proper clean of the system and replacement of the received drier+ expansion device is needed before proceeding to charge the A.C. system with refrigerant.

There are other several problems concerning the compressor:

  • Overheating, you can see the label blistering;
  • Burned Clutch,
  • Short circuit/open coil;
  • Short circuit coil;
  • Condensation problems;
  • A.C. noise diagnosis is a difficult matter. The compressor (like any other machine) creates noise. The noise level inside the vehicle depends on many factors rather than the compressor’s NVH (Noise, Vibration, and Harshness) level itself. A proper design of the A. C system (compressor bracket, hoses, pipes, HVAC insulation, etc.) is the key to avoid noises. In the case of abnormal noise, it is important to try to identify the conditions under which noise appears, the kind of noise, and, the repeatability of the noise under such conditions (define the problem). Examples of conditions: hot/cold days, at certain RPMs, etc. When the compressor has engaged the charge to the engine changes, so it is normal to notice a difference in the quality of the perceived noise.

Remember that the warranty on compressors will only be granted for defects caused during the manufacturing process. Furthermore, FrigAir warranties will not be awarded unless the following procedures carried out:

  1. Before installing the new compressor, the system should be flushed with approved flushing fluid.
  2. The receiver drier/accumulator must be always replaced when mounting a new compressor.
  3. The expansion valve or orifice tube must be replaced because most of the particles or other contamination in the system just blocks the orifice.
  4. New compressors already come supplied with the correct amount and type of oil.
  5. Once the compressor has been fitted, a complete system check should take place to ensure that the pressures are correct, because if the compressor undergoes incongruous pressures it will surely be damaged.

Did we check the leak, clean the system, put a new receiver drier, verified replace the TXV?

(source: Sanden “Compressor failure root causes”)



Remanufactured Compressors

Pre-Season is here.

The Summer preseason is here and we are expanding our A/C catalogue so that we will have a wider availability and we will be more efficient during the busy season.

For this reason, now we can offer three lines of A/C Compressors: OE 920 - Aftermarket 930 - Remanufactured 940, we have over 1.000 references in the catalogue.

The 920 is our mainline and is composed of only of OE Compressors, due to our long partnership with Sanden, we can have always a great availability.

The 930 is our line dedicated to the Aftermarket Compressors, equivalent products to the original.

The 940 is our line of OE Remanufactured Compressors, this line is new and is going to be composed of over 200 references, all the compressors are refurbished in Italy.

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Frig Air offers a different range of Antifreeze, diluted and not diluted. In the catalog, you can find the Traditional and the New Generation series. The traditional series can be used with any type of engine (oil, diesel, or gas), and for every vehicle; you can use the antifreeze properly diluted for the heating systems in buildings situated in particular rigid climates. The New Generation series is suitable for the new aluminum engine and offers new protection against the corrosion of the internal circuit cooling. There are two different New generation liquids Red, suitable for Audi – VW; and Yellow for Renault.





In the DOWNLOADS section of our website, you will find the new AGRI Catalogue, more than 300 references. A/C & Thermal Spare Parts for agriculture vehicles and off-highway machines.
From John Deere to Fendt, discover our line.

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