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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The refrigerant in the automotive system is the substance which not only transfer heat from the passenger compartment in the vehicle to the condenser outside of the car and then released the heat into the atmosphere, but it also cools the compressor down reducing the total heat of compression preventing the compressor from building up excessive pressure and temperature. A poor lubricated compressor could be operating in temperatures that could get up to 800 F
ELECTRONIC CONTROLLED VARIABLE DISPLACEMENT CLUTCHLESS COMPRESSOR AND LACK OF LUBRICATION
Electronic controlled variable displacement compressors could be clutch or clutch-less designs. The ac compressor has a swash plate that rotates to reciprocate pistons, which compress refrigerant. The swash plate is allowed to change its angle which changes the stroke rate of the piston. They are electronically controlled using sensors and an Electronic Control Module (ECM)
Electronic controlled variable displacement compressor is always running even when the a/c is off. The ECM changes the rate of displacement, but the compressor is spinning connected to the drive belt without any clutch to disengage.
Lubrication occurs by using a sump in which the connecting rod splashes oil around the inside of the compressor. Some automotive air conditioning compressors use an oil pump to circulate the oil, like an engine lubrication system. Lubrication is accomplished while the ac compressor is running and there is refrigerant and oil circulating back to the compressor.
The (ECVD) clutch-less compressor should not be operated without refrigerant in the system to carry lubricant.
EXPENSIVE MISDIAGNOSIS AND UNNECESSARY COMPRESSOR REPLACEMENT
These (ECVD) clutch-less compressors do not have a conventional clutch, meaning the compressor shaft turns all the time driven by the accessory drive belt, even when the a/c is commanded off from the hvac temperature control assembly panel!
ECV CONTROL DIAGRAM
2015 HYUNDAI ELANTRA GT 2.0L
Source: ALLDATA Repair.
Variable Swash Plate Compressor
The internally controlled variable swash plate compressor changes the swash plate angle by a MCV (Mechanical Control Valve) in accordance with fluctuation of a suction pressure.
The externally controlled variable swash plate compressor changes the swash plate angle by an ECV (Electric Control Valve) in accordance with an electrical signal from the heater & A/C control unit.
HOW TO QUICKLY DIAGNOSE CLUTCHLESS COMPRESSOR FAILURE
Without the right tools This new compressor output control technology can make it difficult to determine if the poor ac performance is being caused by a computer control malfunction or another problem in the refrigeration system or cooling system of the vehicle. This can result in an expensive misdiagnosis and unnecessary compressor replacement.
These are different tools that could be used for correct testing a diagnose of this units:
1. A scan tool and checking PWM signal from the module to the ECV compressor .
2. Handheld ECV Compressor tester unit to manually control the ECV on the compressor and increase or decrease (PWM) the pumping capacity of the air conditioning.
3. A scope can be used by carefully back probing the connector to the control valve and connecting the scope leads to the two wires and check the PWM wave signal
LOW REFRIGERANT AND LOW OIL CONDITION COULD LEAD TO AC COMPRESSOR DAMAGE
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%.
Car A/C air conditioning compressor clutch bearing.
Automotive a/c compressor clutch bearing failures are usually caused by system problems and not the bearing itself. Replacing the noisy bearing without finding the root of the problem and fixing it permanently will only lead to premature damage of a new component and a waste of time and money. Seals, compressor shaft and bearing could share the same enemy, heat.
What could cause damage to the ac compressor bearing in my car ?
Excessively high temperature and lack of lubrication
Slipping compressor clutches
Over tensioned manual belt tensioners
A leaking compressor shaft seal
A leaking compressor shaft seal could cause the compressor oil to find its way into the hvac compressor clutch bearing contaminating the grease. The properties of the bearing grease will be changed by this oil contamination causing it a poor compressor bearing lubrication and inevitably internal bearing failure.
What could cause the ac system in my car to buildup excessive high pressure and temperature ?
Leaking air conditioning systems will leak out refrigerant and the oil that resides inside of the compressor creating a huge frictional resistance between the compressor piston and the cylinder leading to an increase in compressor internal temperature.
Overcharged or improperly vacuumed auto ac systems will create high system pressures and therefore elevated temperatures.
Compressor pressure plate and rotor pulley excessive air gap will cause slippage and rise in temperature.
Replacing just the bearing
A/C compressor factory bearing defects will not need more than a few hours of compressor operation to become evident. Rarely the bearing itself is the culprit.
Normal noises of the A/C operation include the sounds of A/C compressor clutch engagement, the blower motor, moving blend air and mode doors, and pressure equalization after vehicle is shut down. By early identifying the sound of a bad ac compressor on the vehicle, could make a big difference in terms of labor time and price of the repairs needed.
Noises that could indicate the need for a/c compressor service or replacement include:
Growling noise with compressor disengaged
Growling noise with compressor engaged
Why is my AC making a weird noise?
Banging noise: If liquid refrigerant enters the compressor, a thumping, banging noise will result.
Knocking noise: Heavy knocking compressor noises come from refrigerant system blockage, incorrect pressures, or internal damage.
Growling noise with compressor disengaged: A worn compressor pulley bearing or clutch bearing will cause a growling noise.
Growling noise with the compressor engaged: A/C compressor internal bearings damage.
Squealing noise: A loose, dry, or worn A/C compressor belt will cause squealing noise. This noise will be worse during acceleration.
Worn or dry blower motor bearings may cause a squealing noise when the blower motor is running
Rattling noise: A loose or worn clutch hub or loose compressor mountings bolt will also cause rattling noise from the compressor.
Knocking noises: This type of noise from the compressor usually indicates internal damage, especially on piston-type compressors. Always check the compressor mounting and brackets before condemning the compressor for noise.
A loose mounting can cause knocking noises from the compressor area that may be mistaken for internal compressor noise.
Grinding noise: When car accessories pulley bearings are failing, they can make this kind of noise.
Do you need assistance checking the proper operation of your car ac compressor ?
Analysis of Denso A/C Compressor warranty claims show 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.
Air conditioning oil properly recharged and balanced.
Installing the 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!
A worn compressor pulley bearing, or clutch bearing will cause a growling noise. AC compressor clutch assembly needs to be replaced.
Growling noise with the compressor engaged
A/C compressor internal bearing/components damage. The entire ac compressor should be replaced.
A high compression ratio
Either an increase in head pressure or a decrease in suction pressure will cause higher compression ratios. Any time a system has high compression ratios the compressor’s discharge temperature will also be elevated. This is because of the higher heat of compression during the compression stroke associated with higher compression ratios. When compression ratios are high, more energy is needed to raise the pressure of the suction gases to the discharge pressure. This means more heat is generated as heat of compression during the compression stroke.
Cooling performance decreases
A/C not as cold as it used to be
Knocking noises from the compressor
Squealing A/C compressor drive belt
Excessively hot compressor crankcase
Compressor pressure plate not engaging
Both lines from a/c compressor at the same ambient temperature
Gauge pressure ,High side Low and Low side High
A/C compressor locked up. Compressor Does not turn when rotated by hand.
Compressor pressure plate signs of overheating condition
Compressor body signs of overheating condition
The best way to fix a bad car ac compressor
To permanently fix a bad car ac compressor you must first, take care of the condition that led to the compressor damage. Identifying what damaged the old compressor is the only effective way to prevent the same fault happening to the new compressor. It is vital to follow the proper manufacturer specifications while installing the new a/c compressor or any air conditioning component.
The top automotive system faults that lead to A/C Compressor Damage.
These are the top automotive system faults that could lead to A/C compressor Damage:
A/C compressor over cycling.
Excessive high compressor temperature due to air conditioning system contamination.
Cooling system underperformance affecting a/c operation.
Drive belt slipping on a/c compressor pulley creating excessive high heat load.
Slipping clutch pressure plate due to out of specs compressor clutch gap.
Shorts to power or ground on the ac compressor clutch coil circuit.
A/C compressor clutch relay inoperative or shorted.