The moving parts of a compressor are machined to very fine tolerances, so system cleanliness and correct lubrication are critical. The following procedure must be followed whenever a compressor is serviced or replaced, or whenever component break-down or system contamination is suspected.
Before Installation
1. Check system with an accurate refrigerant analyzer to determine what refrigerant is in the system and if there is any gas cross contamination (including air).
2. If compressor/system still operates, run engine at 1500-1750rpm and check system pressures with the system operating at maximum cooling and fan settings.
3. Check resultant gauge readings against the temperature pressure charts.
4. Establish the cause of failure of the original compressor and rectify the problem. (Remember that most compressor failures are due to system faults, loss of gas, over-gassing etc., not a fault in the compressor itself.)
5. Remove and discard the receiver-drier or accumulator and the TX valve / CCOT.
6. Drain oil from the original compressor and inspect for signs of metal filing contamination, incorrect oil mixtures, black or greyness. If there are any metal filings or grey fine metal in the oil, the condenser must be replaced if it is a multi-flow / parallel flow style as their design deems them un-flushable. If the condenser is a Modine or Tube and Fin style, these may be able to be flushed, providing the flush is emerging clean after the process. In catastrophic compressor failures, evaporators may also need to be replaced if the design means they cannot be flushed sufficiently.
7. Flush system thoroughly with an approved A/C flush solvent such as TO-28729. (‘Purging’ with a refrigerant or dry nitrogen is not sufficient as neither will remove scale, corrosion, acid, oil or contaminants.) Be sure to follow the flushing procedure correctly.
8. Install a new receiver-drier or accumulator and TX valve, as well as the condenser and evaporator if required. Note: parallel flow condensers can’t be flushed.
At Installation
1. Check the oil specification for the system and compressor concerned, and ensure that the correct grade and amount is added where necessary. Never mix or re-use refrigerant oil.
2. Renew all O-rings. Never re-use O-rings.
3. Turn the compressor by hand several times before charging the system.
4. Evacuate and charge the system according to correct procedure and specification for the system and compressor concerned.
5. Ensure that the system is charged with the correct amount of refrigerant. Remember, some systems are easily over-gassed if charged simply by gauge readings and/or sight glass, especially if other variables are not taken into account.
6. Check the system for leaks and ensure that the system operation and gauge readings are normal.
Other Helpful Hints
• Always check the quantity and integrity of the oil in the failed compressor - this is a valuable aid to diagnosing the system fault.
• Check the hoses, receiver-drier and TX valve for signs of contamination and/or break-down (also a useful aid to diagnosis)
• A compressor which will turn by hand after removal, but which was seized on the vehicle, almost always indicates a head pressure problem.