Ace, you need to put more info in your signature line so we know what kind of rig you have and what you are talking about. My 03 has a refrigeration valve used to refill the freon in my rig for the dash air, is this what you are talking about? There is usually a tag attached to it showing how much to add etc. Mine shows 40 ozs of 134a to fill the system. You can buy a can of freon at Walmart to do this if you are having problems. Usually if you are low on freon it means you have a leak but not much cost to try this yourself to see if takes care of your problem. Welcome to the forum also.