A FLIGHT CREW REPORTS PROBLEMS WITH CARRIER COMPANY MESSAGE REQUIRING PILOTS TO MONITOR CABIN PRESSURIZATION FLOW BY THE FLOW LIGHT ON THE PRESSURE CONTROLLER; NOT THE ANNUNCIATOR PANEL LIGHT; ON CERTAIN MD80 ACFT. FLT CREW EXPERIENCED PRESSURE CONTROLLER ANOMALY; ALLEGING 2 DIFFERENT MODELS OF MD80 REQUIRING 2 DIFFERENT PRESSURE CONTROLLERS; SOMETIMES PLACED IN WRONG TYPE ACFT.

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DURING CRUISE; FO WAS READING A COMPANY MESSAGE WHICH REQUIRES PLTS TO MONITOR PRESSURIZATION FLOW ON SOME MD80 ACFT BY THE FLOW LIGHT ON THE PRESSURIZATION CONTROLLER; THE FLOW LIGHT ON THE ANNUNCIATOR PANEL BEING INOP. THIS CTLR HAD A STICKER COVERING UP THE LOW FLOW LIGHT ON THE CONTROLLER WHICH READ 'MAINT USE ONLY.' ON LNDG IN ZZZ; I CALLED MAINT CTL AND EXPLAINED THE PROB. THEY HAD US DO 2 PROCS TO TEST THE FLOW LIGHT; BOTH WHICH DID NOT WORK. THEY ASSURED US THE SYS WORKED; SO WE TOOK THE ACFT BACK TO ZZZ1. MAINT CTL SAID THEY WOULD RESEARCH THE PROB AND INFORM ZZZ1 MAINT. MAINT MET THE ACFT IN ZZZ1; BUT WERE CONFUSED BY THE CONTROLLER SITUATION. AFTER SOME RESEARCH AND SEVERAL PHONE CALLS; IT WAS DETERMINED THAT THIS ACFT HAD THE WRONG CONTROLLER. XYZ CONTROLLERS HAVE THE FLOW LIGHT ON THE CONTROLLER DISCONNECTED AND USE THE FLOW LIGHT ON THE ANNUNCIATOR PANEL. SOME PLANES ARE JUST THE OPPOSITE AND HAVE THE ANNUNCIATOR PANEL FLOW LIGHT AND USE THE FLOW LIGHT ON THE PRESSURIZATION CONTROLLER. THIS ACFT HAD AN XYZ CONTROLLER; MAKING BOTH FLOW LIGHTS INOP. MY CONCERN IS THAT THERE ARE MORE MD80'S WITH THE WRONG PRESSURIZATION CONTROLLER AND THAT A DEPRESSURIZATION AND EMER DSCNT WILL BE DONE BECAUSE THE CREW HAD NO WAY TO MONITOR PRESSURIZATION FLOW. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: REPORTER STATED HIS CARRIER ACQUIRED DIFFERENT CONFIGURATION MD-80'S THAT HAVE BEEN BLENDED INTO THE REST OF THEIR MD-80 FLEET. THESE ACQUIRED MD-80'S USE THE FLOW LIGHT ON THE PRESSURE CONTROLLER TO MONITOR CABIN PRESSURIZATION LOW AIR FLOW; BECAUSE THE FLOW LIGHT ON THE ANNUNCIATOR PANEL HAS BEEN MADE INOP. THEIR STANDARD CONFIGURATION MD-80'S ARE JUST THE REVERSE; BECAUSE THESE ACFT HAVE THE PRESSURIZATION FLOW LIGHT ON THESE PRESSURE CONTROLLERS INOP AND USE THE ANNUNCIATOR PANEL FLOW LIGHT TO MONITOR CABIN PRESSURIZATION LOW AIR FLOW. REPORTER STATED THESE TWO DIFFERENT PRESSURIZATION FLOW MONITORING REQUIREMENTS ALSO REQUIRE TWO DIFFERENT TYPES OF PRESSURE CONTROLLERS. THEY ARE NOT INTERCHANGEABLE. ACFT ARE BEING FOUND WITH INCORRECT CONTROLLERS INSTALLED. AS A RESULT; NEITHER OF THE FLOW LIGHTS WILL BE FUNCTIONAL. THIS REQUIRES THE PILOTS TO FLY USING MANUAL MODE OF PRESSURE CONTROLLER OPERATION BECAUSE THE CREW HAS NO WAY TO MONITOR LOW PRESSURE FLOW. REPORTER ALSO STATED THE MD-80'S HAVE A TENDENCY IN ICING CONDITIONS TO HAVE LESS PACK AIRFLOW. THIS; COUPLED WITH THE TAIL PITOT TUBE TENDING TO ICE OVER; CAUSES THE PACKS TO SHUT DOWN IN FLIGHT.