The test cart is used to simulate a vehicle (based on volume and heat transfer area). With the hand valve closed, the cart simulates a closed (leak-free) vehicle A/C system. With the hand valve open, the cart simulates a vehicle A/C system with a leak. To use the cart, connect the tools to appropriate fittings and either open or close the hand valve to simulate the desired state. The cart is equipped with a safety pressure relief valve, which will relieve pressure above 500 psig.