Robinair 16916 - R-1234yf Oxygen SensorReplacement oxygen sensor for Robinair R-1234yf machines and refrigerant identifiers. Your 1234yf machine or identifier should provide advance notice when the oxygen sensor is nearing the end of its lifespan. Oxygen sensor replacement is required to return the machine to normal operation. If the oxygen sensor expires, neither the integrated identifier nor the machine is able to recover or add refrigerant to the internal tank. See the Owners Manual Maintenance section for instructions on how to replace the oxygen sensor. Replacement filter for:AC1234-4AC1234-4SLAC1234-4-230AC1234-6AC1234-916990/16995 Refrigerant identifier