Valves are not included on any small refrigerated appliance. Refrigerators don't have valves on them either. A technician has to install the valves, when the system needs to be checked. To check a seal system, it will require a certified technician with the proper equipment. A technician should be able to give you a cost estimate, before repairing the product. You can have a technician out to your house to check this or you can take it in and save a service call. I'm adding a link you can check, to get it serviced at your home or take in. Here is a link for the website:
Sears Home Services
. If you need more assistance, please resubmit your question, with additional details.