A B737-200 MADE AN UNSCHEDULED LNDG DUE TO BOTH THE CAPT'S AND FO'S ALTIMETERS WERE INOP.

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THE PLTS WROTE A SQUAWK DURING ITS TEST HOP THAT THE STANDBY PRESSURIZATION WAS INOP. DURING OUR TROUBLESHOOTING; WE DETERMINED THAT THE PRESSURE CTL MODULE WAS NOT RECEIVING BAROMETRIC INFO FROM THE COPLT'S ALTIMETER. WE SWAPPED THE CAPT'S AND FO'S ALTIMETERS TO ISOLATE THE FAULT. WHEN IT DIDN'T CORRECT THE PROB; WE PUT THEM BACK INTO THEIR ORIGINAL POS TO CONTINUE TROUBLESHOOTING. KNOWING THAT WE WOULD PROBABLY HAVE TO REMOVE THEM AGAIN TO CHK FOR VOLTAGES; WE ONLY CONNECTED THE ELECTRICAL CONNECTORS AND SLID THEM INTO POS. FURTHER INVESTIGATION REVEALED THAT THE PROB WAS A BAROMETRIC SELECTOR SWITCH IN THE P-5 OVERHEAD PANEL. AFTER THE PROB WAS CORRECTED; WE PERFORMED THE ADJUSTMENT/TEST PROC; MAINT MANUAL; FOR THE STANDBY PRESSURIZATION SYS CHK AND THE OPERATIONAL CHK FOR THE ENTIRE PRESSURIZATION SYS. WHEN THIS WAS COMPLETE; THE ONLY THING LEFT WAS TO CLOSE AREAS OPENED. AT THIS POINT WE SLID THE ALTIMETERS BACK INTO POS; AND SECURED THE SCREW CLAMPS. THE QUICK DISCONNECTS WERE NOT RECONNECTED. WHEN THE ACFT TOOK OFF; THE ALTIMETERS DETECTED A DISCREPANCY BTWN THE BAROMETRIC INPUTS AND THE CADC'S ELECTRONIC READINGS. WHEN THIS HAPPENS; THE ALTIMETERS AUTOMATICALLY DEFAULT TO THE BAROMETRIC INPUTS. SINCE BOTH BAROMETRIC HOSES WERE DISCONNECTED; THE ALTIMETERS WERE IN EFFECT 'DEAD.' THE ACFT HAD TO MAKE AN UNSCHEDULED LNDG. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATES THEIR CONCENTRATION WAS ON THE CABIN PRESSURIZATION SYS PROB AND WHEN ASSIGNED ANOTHER JOB THEY COMPLETELY FORGOT THE ALTIMETERS BEING INSTALLED; BUT NOT CONNECTED TO THE STATIC LINES. WHEN ASKED IF A LOW RANGE LEAKAGE TEST WOULD HAVE DISCLOSED THE UNCONNECTED STATIC LINES; THE RPTR ADVISED THAT THE COMPANY POLICY IS NO TEST IF A QUICK DISCONNECT FITTING IS PRESENT. IF ACTUAL THREADED TUBING LINES ARE OPENED THEN A TEST IS REQUIRED. AN ALERT BULLETIN AUTHORED BY THE RPTR WAS SENT TO ALL STATIONS THROUGHOUT THE SYS WITH DETAILS OF THIS INCIDENT. THE FAA HAS CONTACTED THE RPTR.