And how do you know that it is right?. Regardless all refrigeration works on the same principle. , A gas with a low boiling point is compressed and cooled to a liquid. It then is metered at a low pressure so that it can absorb heat to flash back to a gas. Metering can be a expansion valve or a restriction like a cap tube. However, you must have air flow over both the evaporator and condenser enough to transfer the heat. So, we have determined that you need refigerant, air flow, and a pressure differential. Which one don’t you have?