To check the auto a/c compressor compression ratio, note on paper the low and high side gauge readings and add atmospheric pressure to both readings. Divide the high side reading (with the atmospheric pressure added) by the low side reading (with the atmospheric pressure added).The result should be between 6.5:1 and 7.5:1. A compression ratio of 8:1 or higher may cause compressor failure. Learn More…
The A/C compressor is considered the heart of the refrigeration system. Compression ratio is the technical expression for pressure difference. Compression ratios are used to compare pumping conditions for a compressor and is an efficient way to evaluate the health of an air conditioning compressor.
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How to find an auto ac compressor problem, before is too late?
Check for high compression ratios. To check a/c compressor compression ratio, note on paper the low and high side gauge readings and add atmospheric pressure to both readings. Divide the high side reading (with the atmospheric pressure added) by the low side reading (with the atmospheric pressure added).The result should be between 6.5:1 and 7.5:1. A compression ratio of 8:1 or higher may cause compressor failure.
The amount of auto air conditioning system oil and the correct type for the vehicle is vital to the life of the a/c compressor. Proper lubrication is a must for ac compressor long life. When the a/c compressor is operated ,oil gradually leaves the compressor, and the oil is circulated through the entire ac system together with the refrigerant. After the air conditioning system is operated for the first time an oil balanced condition is reached in which a certain amount of oil is retained in the compressor and a certain amount is re-circulated through the ac system components with different amounts of oil depositing in them . If a component of the system is replaced after the system has been operated, we need to compensate for this by adding oil to the new replacement ac part.
HOW AN OVERCHARGE/UNDERCHARGE A/C OIL CONDITION AFFECT THE A/C SYSTEM?
Too much oil in the a/c system could result in extremely high head pressures which will cause poor air conditioning performance and premature wear and failure of the hvac compressor. If there is a surplus of oil in the system, too much oil circulates with the refrigerant ,causing the cooling capacity of the system to be reduced and the compressor head pressure to increase. Too little oil results in poor lubrication of the compressor and an increase in the heat of compression which shorten the life of the ac compressor.
OIL BALANCING AN AC SYSTEM
When there has been excessive leakage of refrigerant, or it is necessary to replace a component of the refrigeration system oil balancing is necessary to assure that the total oil charge in the system is the correct one after the leak has been repaired or the new ac part is installed in the car.
HOW TO OIL BALANCE MY CAR AC SYSTEM
The recommended procedure step by step
Measure the oil recovered from the system while recovering the refrigerant prior to part replacement
Drain and measure the oil left in the old part
Drain the new part(if factory oil-prefilled)
Refill the new part with the same amount of oil removed from the old part and the amount of oil recovered from the system
WHAT TYPE OF OIL ACCORDING TO TYPE OF REFRIGERANT R-12 R-1234YF AND R-134a
The refrigerant oil required by the automotive ac system depends on a number of factors ,but it is primarily dictated by the type of refrigerant used in the system.R-12 car systems used a mineral oil. Mineral oil mixes well with R-12 without breaking down and losing its lubrication characteristics. Mineral oil however cannot be used to lubricate ac systems with R-134a refrigerant.R-134 systems require a different synthetic oil,polyalkylene glycol (PAG).There are different blends of PAG and POE oil; always use the recommended by the vehicle manufacturer or the replacement part manufacturer.
The lubricant oil used in automotive air-conditioning systems is a non-foaming, sulfur free grade specially formulated for use in cars a/c systems. New refrigerants like R-1234yf might use PAG 46 and are backwards compatible for use with R-134a systems, but the R-134a old PAG 46 oils are not forward compatible with R-1234yf systems.
Add the recommend refrigerant oil in the amount listed if you replace any of the following parts:
A/C condenser(including receive Dryer.
25 mL (5/6 fl oz)
Evaporator
40 mL (1 1/3 fl oz)
Line or hose
10 mL (1/3 fl oz)
Receiver/dryer
10 mL (1/3 fl oz)
Leakage repair
25 mL (5/6 fl oz)
A/C compressor
For A/C compressor replacement, subtract the volume of oil drained from the removed A/C compressor from 82 mL (2 3/4 fl oz), and drain the calculated volume of oil from the new A/C compressor: 82 mL (2 3/4 fl oz) － Volume of removed A/C compressor = Volume to drain from new A/C compressor. NOTE: Even if no oil is drained from the removed A/C compressor, do not drain more than 50 mL (1 2/3 fl oz) from the new A/C compressor.
Some compressor clutch circuits contain a thermal limiter switch that senses compressor surface temperature. Some A/C compressor clutch circuits also contain a low-pressure cutoff switch. These are auto ac protection devices and their goal is the auto ac compressor protection.
A/C safety switches .
A/C systems have load-sensitive electrical switches; such as the low-pressure switch, high-pressure switch, pressure cycling, and power steering. Not all the switches, however, are used in all vehicles. The pressure switches are used to prevent compressor or component damage in the event of extremely high or low-system pressures.
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Thermal switches are used on both the low and high side of AC systems. A Thermal switch may be connected in series with the compressor clutch.
A/C compressor cycling control .
A thermostatic switch de-energizes the clutch and stops the compressor to keep the evaporator from freezing up. When the temperature of the evaporator approaches the freezing point (or the low setting of the switch), the thermostatic switch opens the circuit and disengages the compressor clutch. The compressor remains inoperative until the evaporator temperature rises to the preset temperature, at which time the switch closes and compressor operation resumes.
A/C Compressor temperature control.
A thermal limit switch may be mounted on or near the compressor and is used to stop compressor operation before the temperature of the compressor reaches a point of damage.
Most vehicle manufacturers recommend closed loop flushing with air conditioning refrigerant as a flushing agent. A benefit of this type of flushing is there is no danger of flush contamination, since the flush agent being used is the correct refrigerant for the automotive A/C system.
Non-Approved Automotive AC flushes
Non-Approved flushes : Over the years many different liquids have been used as a non-approved flushes for A/C systems. The more common items are:
Alcohol
Brake cleaner
Carburetor cleaner
Mineral spirits
Penetrating oil
R-11, R-22, R-113
Gasoline
Automotive AC system contamination with liquid flush agents
The use of unapproved chemical flushes can result in damage to rubber components in sealing washers , compressor shaft seals , O-rings and hoses.
Automotive A/C compressor internal damage
Unapproved chemical flushes when mixed with the auto ac compressor oil , it will alter the viscosity of the oil as well. Any material left behind in the a/c system after flushing will dilute the lubricant and cause performance issues , increased compressor noise and premature compressor failure. If compressor failure is caused by non-approved flushing agent being left behind in the a/c system it can void the compressor warranty.
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Replacing an A/C condenser with missing or bent fins.
Keeping the Cooling system performing at 100 % efficiency
Checking the Cooling system fan clutch or electric fans operating at 100 % efficiency
A/C refrigerant system free from air or other contaminations.
Protect Auto A/C compressor against lack of lubrication.
With a large refrigerant undercharge, oil is pumped out from the compressor and becomes trapped in the evaporator or other ac components of the system and is unable to properly return to the hvac compressor. The amount of oil in the compressor can get down to dangerously low levels creating excessive heat and, in most cases, leading to failure of the unit. Some Air conditioning tests has shown that with an undercharged ac system, the oil amount in the compressor was reduced by over 57%.
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