What was found
A PASSENGER DOOR OPEN INDICATION ON THE RWP. DISP WAS RELAYING INFO TO MX CONT WHO WAS GUIDING THE CREW THROUGH A PRESS PROBLEM. CREW REPORTED THAT PRESS WAS CLIMBING AROUND 1200 FT P/MIN, CAB PRESS NOT ALT. MX CONT INSTR CREW TO SWITCH FROM AUTO TO MAN, BEFORE THE CREW COULD SWITCH THE A/C PRESS WAS DESCENDNG AND THE LIGHT EXTINGUISHED. CREW DISCUSSED DIVERT BUT MX CON SAID IF DOOR IS SHUT AND LOCKED WITH NO LOSS OF PRESS IT IS A INDICATION PROB. CREW CONT, PRESS STABILIZED AND NO FURTHER INCIDENT THE REST OF FLT. IN PHL CREW TBLSHOT PRESS PROB W/MX CON BY OPENING AND CLOSING DOOR. COULD NOT DUPLICATE FAILURE. NO OTHER PROBLEM REST OF FLIGHT.