Normally, an A/C system is charged on which side with the engine running?

Charging an A/C system is typically done on the low side as a vapor, and this method is widely recommended for several reasons. When the engine is running and the A/C system is in operation, the low-pressure side of the system should be charged with refrigerant in its vapor form. This is crucial because it allows for the refrigerant to effectively enter the evaporator coil, where it can absorb heat from the cabin air.

Charging on the low side ensures that the refrigerant can vaporize properly, helping to avoid liquid slugging, which can damage the compressor. In addition, when the A/C is running, the low side of the system has a lower pressure, creating the perfect environment for the vaporized refrigerant to be pulled in by the system.

It is essential to monitor the low side pressure to avoid overcharging, which could cause the system to malfunction. This correct charging method not only maximizes the efficiency of the A/C system but also protects its components. Proper understanding of the principles of refrigeration and the flow of refrigerant are pivotal in HVAC maintenance and repair.