Auto A/C Compressors have evolved over time and the old, fixed displacement compressor has been replaced by more efficient variable displacement compressors. Pressure controlled variable displacement compressor and Electronically Controlled Variable Displacement Compressor (ECV) react in different ways compared to fixed displacement compressors when air conditioning restrictions and other common automotive a/c faults happen. Failure to identify the type of a/c compressor in the vehicle at the beginning of the diagnostic procedure could lead to unnecessary, expensive and in most cases time consuming repairs. A restricted Thermal Expansion Valve creates Manifold gauge readings that could lead to chasing a/c system leaks, unnecessary auto a/c compressor and sensor replacement.
How do I know if my compressor or expansion valve is bad?
Manifold Gauge readings
Low side LOW High side LOW
A restricted Thermal Expansion valve gauge readings will be different in the newer Pressure controlled variable displacement air conditioning compressor.
When a restriction in the refrigerant flow caused by a Thermal Expansion Valve (TXV) fault happens, the Pressure controlled variable displacement compressor will try to compensate the change in refrigerant pressure from the TXV by adjusting the compressor internal control valve, and keep the compressor crankcase pressure at a value where the swash plate angle based on the low side pressure is prevented from going into the condition where you see a manifold gauge vacuum reading. The manifold gauge reading in this type of system will show Low side gauge reading low and High side gauge reading low. It could be erroneously diagnosed as a weak compressor problem.
Low Side into Vacuum High Side LOW
A restricted Thermal Expansion Valve (TXV) gauge reading on an Electronically Controlled Variable Displacement Compressor will be different due to the logic the Powertrain Control Module uses to operate and control the a/c compressor. The PCM will receive inputs from the evaporator temperature and will command signals to the ac compressor electronic control valve to adjust pumping capacity accordingly. When the TXV fails or is restricted the evaporator temperature will increase and that increase value will be sent to the PCM which in turns will increase compressor pumping capacity to 100%.The Electronically Controlled Variable Displacement Compressor will operate similar to an old ,Fixed Displacement A/C Compressor and the Manifold Gauges will show Low Side going near 0 Psig or into a vacuum reading.
How do I know if my compressor or expansion valve is bad?
The type of system must be identified
The type of a/c compressor must be identified
Manifold Gauge Readings must be checked
PWM signals to the ECV must be inspected
Avoid unnecessary expensive repairs.
The air entering the cab is only slightly cool, and there are bubbles visible in the sight glass. there is usually about an 95% chance the restriction is expansion valve failed in the closed position related, 4% chance it is drier related and 1% chance it is somewhere else along the system or an internal drier desiccant bag rupture leading to a/c system contamination and restricting the metering orifice of the expansion valve.
Inaccurate refrigerant(freon) charges increase the chances of auto ac compressor lock up. Modern auto a/c systems require super accurate charging. Being off as little as 2 ounces can cause problems.R-134a and R-1234yf ac system tolerances require charge rates that must remain or should be charged within +/- 5% of OEM recommendation. SAE J2788 requires charge accuracy of +/- one-half ounce.
Attempting to charge by cans is History !!
Car ac compressor lock up due to improper compressor lubrication.
Refrigerant moves the oil inside the ac system and helps to cool down the ac compressor. An undercharge or overcharge refrigerant condition will increase the air conditioning compressor temperature and a change in oil viscosity and lubrication characteristics. Most compressor lock ups are the result of a lubrication problem.
AC compressors lock up due to ac system contamination
Auto ac compressor damage may occur because of system contamination. Anything more than the correct type of freon and oil is a contaminant. The use of sealers to fix small refrigerant leaks will cause oil and refrigerant contamination and ultimately ac compressor lock up. Sealer can’t be removed from the A/C systems. The contaminated components must be replaced.
The use of excessive Dye to help finding leaks in the ac system could create a contamination problem as well, increasing the normal working pressure of the ac compressor and the overall efficiency of the air conditioning system.
Improperly replacing any component in the automotive air conditioning system where the system must be opened for replacement of the damaged part and not evacuating the system before recharging it with the proper amount and type of refrigerant will contaminate the ac system with air. Air and moisture inside the system will create excessively high operating pressures and temperatures and eventually could lead to a compressor lock up.
Inefficient ac condensers and air conditioning compressor lock up
Debris on the condenser will affect the desuperheat, condensation and subcooling processes happening in the auto ac condenser.AC condenser with bent or missing fins will be unable to efficiently operate. An inefficient ac condenser will cause an auto ac compressor to lock up.
Low Refrigerant charge and electronically controlled compressor lock up ?
The car engines in vehicles with the clutchless compressors should not be run without refrigerant in the A/C system. Without refrigerant to move the oil, the auto ac compressor may not be properly lubricated and compressor lock up may result.
Do you need assistance inspecting the state of your ac compressor in your vehicle?
Incorrect or contaminated refrigerant in the air conditioning system.
Inefficient or restricted auto a/c condensers
High compression ratios
What to do if my auto A/C Compressor fails ?
Technically the compressor can be rebuilt ,it is recommended to replace the entire compressor. If there was a major internal compressor failure the entire system must be inspected for debris(metal from internal compressor components).After an internal compressor failure, it is recommended to replace the A/C condenser(Specially if it is a modern Parallel Flow type) and the drier, to avoid contamination of the brand new air conditioning compressor. Also, the system should be flushed to avoid contamination.
Many auto ac compressor manufacturers list the oil amount on the label usually on the hvac compressor itself, but not all. Some may show it on the under hood sticker in the engine compartment. The best and most reliable way to determine the exact amount of oil in the new car ac compressor is to drain the new ac compressor and measure the amount of oil if any, inside.
Do you need assistance balancing the oil in your car ac compressor ?
Call Us today ! One of our ASE certified car ac mechanics will come to your home or office. We have car ac mechanics near you.