Moisture contamination refers to a failure that results from conditions that can occur when moisture is introduced into the A/C system.
The A/C compressor is designed to perform efficiently under specific controlled conditions. If contaminants are introduced into the system they act to reduce compressor efficiency, effectiveness, and durability.
Moisture as used in this context refers to water in any form (solid, liquid, or gas). When moisture is introduced in the A/C system, it may combine with the system refrigerant to form an acidic solution which can erode internal compressor components. In this case, moisture does not cause direct compressor failure; the failure results from the failure of a part that has been weakened as a result of the effects of rust and/or corrosion.
Moisture can create ice at the expansion valve level which can cause erratic functioning of the valve. As a consequence of this malfunction, a liquid refrigerant arrives at the compressor or a low amount of the refrigerant/oil mixture arrives at the compressor.
Moisture can also cause corrosion of internal parts, such as the valve plate.
During normal compressor operation, the pistons compress refrigerant gas in the cylinders. Moisture in the system can lead to liquid slugging.
Liquid slugging is a condition that occurs when liquid is allowed to enter one or more cylinders. Because the liquid is practically non-compressible, the compressor seals may be compromised when the pistons attempt to compress the liquid. Liquid slugging can lead to permanent valve damage and reduced compressor efficiency.
Moisture contamination occurs as a result of moisture being allowed to enter and remain in the A/C system.
This condition can be caused by the following:
• Improper vacuuming of the system.
• Contaminated system components.
• Contaminated refrigerant and/or oil.
• Saturated or malfunctioning drier.
• Water permeability through the hoses.
• Leaving uncapped hoses or any A/C components exposed to the air for long periods of time.
• Leaving the suction/discharge caps off the compressor
• Receiver drier must be replaced according to A/C system manufacturer-recommended service period.
There are 4 primary identifiers of moisture contamination.
1. Contaminated Oil = Contaminated oil is identified by its color.
Clear/yellow oil - new or used oil.
Light grey oil - Common within the first few hours of use.
Light green/yellow oil - oil contains a leak detector additive.
Silver/grey oil - indicates the presence of larger metal particles in the oil.
Black oil - small metal particles are present in the oil.
Brown oil (carbonized oil) - the A/C system has overheated due to condenser malfunction, blockage or air flow restriction through the condenser, defective pressure switch, or lack of oil/refrigerant.
Orange oil (this is applicable only to Sanden oil) - the oil has become contaminated by humidity.
2. Rust = Rust may occur on internal steel compressor components that are exposed to moisture for extended periods.
3. Slugged Valves = A slugged valve is one that has been permanently deformed as a result of liquid slugging.
4. Copper Plating = The presence of copper plating generally occurs when there is a high moisture content in the A/C system.