Then go clockwise using consecutive numbers. Return the analyzer to NST for calibration and replacement of oxygen cell. If it is less than twelve months since last calibration the oxygen cell is covered under the manufacturer's warranty.
Most likely problem is particulate matter in valve path.
Click here for instructions on how to correct this problem. You should bleed the gas line before testing outlets if excess moisture is present in the gas lines. Take a gas adapter for the appropriate type gas and connect it to the outlet without connecting the adapter to the gas hose. Place your hand in front of the outlet and allow free flow of gas until no moisture appears on your hand. This is not necessary for every outlet.