Does the A/C system have to be vacuumed before recharging?
Yes, the A/C system should always be vacuumed before recharging. Vacuum removes air and moisture from the system. Removing moisture is important as it creates harmful acids when mixed with the refrigerants. Those acids will corrode the system internally and can cause restrictions at the orifice tube. On the other hand, air causes problems with high pressures and is very difficult to diagnose when it’s in an A/C system. The air is considered a contaminant and is a ‘non condensable’ Therefore, it will be trapped at the top of the condenser. The only sure way to remove the air is to vacuum the system before recharging, and always be sure the hoses on your gauge set are purged of air.
