What typical effect would charging an R-12 system with R-22 have on the compressor?

Charging an R-12 system with R-22 can lead to significant issues due to the differing properties of these refrigerants. R-12, a chlorofluorocarbon (CFC) refrigerant, and R-22, a hydrochlorofluorocarbon (HCFC), have different pressure-temperature characteristics and lubrication requirements. When R-22 is introduced into an R-12 system, the compressor is likely to face overheating due to inadequate lubrication. R-12 systems are designed to work with oils that are compatible with R-12, while R-22 may not properly dissolve in that oil, leading to diminished efficiency and increased heat generation within the compressor.

This overheating can cause the compressor to operate outside of its intended parameters, potentially resulting in mechanical failure or reduced lifespan. Additionally, the pressure changes that occur from using a refrigerant not designed for the system can exacerbate these issues, making overheating a serious risk. Therefore, introducing R-22 into an R-12 system is likely to cause significant harm to the compressor due to overheating, making it the correct answer to the question.