When I charge my AC the coolant blows back out the pressure switch ? Would this be a bad pressure switch or the result of something else?

 

Sometimes the o-rings or hoses leak and have to be replaced. Have you been using a set of refrigeration pressure gauges? If there is too much refrigerant, then the high pressure safety valve may rupture or something may break. Also, after a system has been opened, it must be evacuated with a vacumn pump to remove moisture and air, before recharging. In some cases, the filter dryer must be replaced and the system may require flushing. You need to follow the instructions in the Audi shop manual CD from BentleyPublishers.com.