In which scenario would you need to use nitrogen in the AC system?

Using nitrogen in the AC system is primarily associated with pressure testing for leaks. This is because nitrogen, being an inert gas, can be safely introduced into an AC system to pressurize it without running the risk of reacting with any of the system's components or refrigerants. When nitrogen is applied, it allows technicians to monitor for any pressure drops over a specified period. A drop in pressure indicates a leak, as the nitrogen should remain at a constant pressure if the system is intact.

This process is critical in ensuring the integrity of the AC system before introducing refrigerants. Proper leak testing with nitrogen is an industry-standard practice, allowing for the confirmation that the system can hold pressure and is free from leaks before proceeding with refrigerant charging and operation.