Some vehicles hold their refrigerant better than others.. In the instance the vehicle has no refrigerant at all, Southern Mobile Aircon will perform a nitrogen leak test to pressurize the system and find any potential leaks. This is an environmentally friendly solution as refrigerant is harmful to the environment where as nitrogen is harmless. If the system passes the pressure test it can then be filled with refrigerant. If refill is done at time of test there will be no charge for pressure test. *no charge if system passes pressure test and refill carried out