You'll need some refrigerant guages that'll cost anywhere from $85 upwards. First though you would need to check and see if it even has the service ports to connect the guages to. Depending on the type of refrigerant you will not be able to buy it unless you have a CFC certification and then a 30 lb jug is $200 or more. You should probably get someone to check it for you. With the price of components and service calls it's usually cheaper to get a new unit but you could call and get some prices for service calls first. Sorry to give you this bad news.
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You'll need some refrigerant guages that'll cost anywhere from $85 upwards. First though you would need to check and see if it even has the service ports to connect the guages to. Depending on the type of refrigerant you will not be able to buy it unless you have a CFC certification and then a 30 lb jug is $200 or more. You should probably get someone to check it for you. With the price of components and service calls it's usually cheaper to get a new unit but you could call and get some prices for service calls first. Sorry to give you this bad news.