A B737-300 CAPT RPTS ON THREE DAYS OF ELECTRONIC EQUIP FAILURES CAUSED BY WATER ENTERING THE E&E COMPARTMENT THROUGH THE AIRSTAIRS DOOR LEFT OPEN IN HEAVY RAIN.

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WHILE TAXIING TO THE RWY IN ZZZ1; FO NOTIFIED 'FAS PLEASE BE SEATED.' NO RESPONSE WAS HEARD IN THE COCKPIT. I THEN REPEATED THE COMMAND; NO RESPONSE AGAIN. I SWITCHED COM PANEL TO FLT INTERPHONE AND RANG THE ATTENDANT CALL CHIME. FLIGHT ATTENDANT INFORMED ME THAT SHE HAD SIGNALED BOTH TIMES. AFTER SEVERAL MORE ATTEMPTS; THE CHIME SIGNAL WORKED. WE THEN WERE CLEARED FOR T/O. ENRTE; THROUGH ZZZ2 CTR AIRSPACE; WE WERE GIVEN CLRNC TO 'CLB AND MAINTAIN FL230.' AT SOME POINT DURING CLB; ZZZ2 CTR REPORTED CONVERGING TFC 'TFC; TWO O'CLOCK AT FL240.' THIN CLOUDS TO THE RIGHT OF OUR COURSE ONLY OBSCURED VISIBILITY SLIGHTLY. ALTHOUGH WE WERE VMC THE WHOLE TIME; MY FO REMAINED ON INSTRUMENTS DUE TO NIGHT CONDITIONS. I WAS WATCHING TCAS AND OUTSIDE VISUALLY. FO WAS FLYING PLT AND I WAS MONITORING. THE AUTOPLT WAS ENGAGED AT THE TIME DURING OUR CLB TO FL230. MOONLIGHT WAS BRIGHT ENOUGH TO ILLUMINATE THE TOPS OF THE THIN CLOUDS TO OUR RIGHT. AS I RECALL; ZZZ2 CTR ALSO RPTED OUR POSITION TO THE TFC. I RECALL THAT WE HAD JUST PAST FL220; AND BOTH OF US CONFIRMED VERBALLY; 'FL220; CLBING 230.' THE ACFT WAS CLBING AT APPROX 1800 FPM VSI EMPTY; WHEN TCAS ISSUED A 'TRAFFIC'; IMMEDIATELY FOLLOWED BY 'CLIMB' RESOLUTION ADVISORY (RA); WITH A FLT DIRECTOR PITCH UP. AT THIS COMMAND OF TCAS; I BELIEVE THAT THE AUTOPLT WAS DISENGAGED BY EITHER MY FO; OR BY ITSELF. THE FLT DIRECTOR COMMAND BARS BEGAN AN INCREASE IN PITCH TO COMPLY WITH TCAS DIRECTION. THIS OCCURRED AT APPROX 22600 TO 22700 FT. AT SOME POINT; THE OTHER ACFT'S LIGHTS WERE TURNED ON; AND I VISUALLY MADE CONTACT. IN THE TIME IT TOOK FOR ME TO ACQUIRE AND VERBALLY CALL 'TFC IN SIGHT!'; MY FO (FOLLOWING THE RA) HAD JUST BARELY PAST FL230. SINCE I HAD VISUALLY ACQUIRED THE TFC; I IMMEDIATELY INSTRUCTED HIM TO IGNORE THE 'CLB' COMMAND FROM TCAS; AND TO LEVEL BACK TO FL230. MY BEST ESTIMATION IS THAT OUR ACFT EXCEEDED FL230 BY NOT MORE THAN 350 FT BEFORE THE VSI INDICATED FO'S DOWNWARD CORRECTION TO FL230 AS PER MY COMMAND. I NOTED THE TIME TO BE APPROX XA:47 ZULU AT THE TIME OF THE RA. I RECALL MAKING A COMMENT ABOUT THE ERRONEOUS TCAS COMMAND TO 'CLIMB'; AND THEN WATCHED TFC TO ENSURE ADEQUATE SEPARATION. CTR CTLR DID NOT QUERY US ABOUT ALT DEVIATION. I ATTEMPTED SEVERAL TIMES TO CONTACT CTR; BUT DUE TO OTHER RADIO TFC ON THE FREQ; THERE WERE A FEW MOMENTS OF UNSUCCESSFUL COMMUNICATION. IT WAS ONLY AFTER I SUCCESSFULLY BROUGHT IT TO HIS ATTENTION; THAT WE HAD RECEIVED AN RA; THAT THE MATTER WAS TRANSMITTED. CTR GAVE US A FREQ CHANGE; AND UPON CONTACTING THE NEXT SECTOR; I REQUESTED A PHONE NUMBER FOR THE PREVIOUS CTLR TO LATER DISCUSS THE MATTER. I MADE NOTE OF THE PHONE NUMBER HE PROVIDED; AND WE CONTINUED THE FLT ON COURSE. MY FO AND I BRIEFLY DISCUSSED THE STRANGE NATURE OF THE 'CLB' COMMAND; AND WE WERE PUZZLED AS TO WHAT HAD JUST HAPPENED. OTHER DUTIES REQUIRED OUR ATTENTION; SO WE DROPPED THE DISCUSSION. WHEN WE FINALLY WERE HANDED OFF TO THE APCH CTL; WE WERE VECTORED FOR A VISUAL APCH TO RWY 7'S FINAL APCH COURSE. THE RADIO AIRWAVES WERE VERY QUITE AT THE TIME OF NIGHT. AS FO CONTINUED ON FINAL APCH; APPROX 18 DME FROM THE END OF THE RWY; WE WERE ISSUED A TRAFFIC ADVISORY (TA) BY TCAS. THE DISPLAY SHOWED A TARGET AT ABOUT 5 MILES AND 1000 FT BELOW. I ASKED THE APCH CTLR ABOUT THE 'TFC'; AND HE INFORMED ME THAT WE WERE THE 'ONLY TFC IN THE AREA' AND THAT WE WERE 'CLRED FOR THE VISUAL RWY 7.' THE 'TFC' THAT TCAS DISPLAYED WAS ON THE SCREEN FOR A FEW MORE SECONDS; AND THEN SIMPLY DISAPPEARED. I READ BACK THE CLRNC THE CTLR HAD ISSUED; AND MADE THE COMMENT THAT WE LOST THE 'TARGET THAT WE WERE PAINTING ON TCAS.' THE RADIO WAS SILENT FOR A MOMENT OR SO; AND THEN INSIDE OF 10 DME; WE WERE 'CLRED TO LAND.' ALL FINAL LNDG CHECKS WERE ACCOMPLISHED; AND MY FO LANDED WITHOUT INCIDENT. UPON COMPLETION OF THE SHUTDOWN CHKLIST; MY FO AND I BEGAN DISCUSSING THE PREVIOUSLY MENTIONED EVENTS CONCERNING TCAS. FO MENTIONED TO ME THAT BEFORE I GOT TO THE COCKPIT; HE HAD PERFORMED A GPWS TEST AND A TCAS TEST.THE TCAS TEST; ON FIRST ATTEMPT DID NOT FAIL; NOR DID IT PASS. IT SIMPLY DID NOT RESPOND. WHEN HE PUSHED THE BUTTON THE SECOND TIME; 'TCAS SYSTEM TEST-PASS' WAS HEARD. WE WERE BOTH STILL CONCERNED THAT SOMETHING WAS NOT RIGHT IN AS MUCH AS WE FELT UNSURE OF THE TCAS SYSTEM'S ABILITY TO GIVE PROPER AND APPROPRIATE GUIDANCE INFO. I THEN CALLED THE PHONE NUMBER GIVEN TO ME BY ZZZ2 CTR; AND SPOKE WITH THE SUPV. HE SAID THAT I WOULD NEED TO CONTACT THE Q&A DESK LATER TO GET ALL THE DETAILS CONCERNING THE ALT DEV. I DISCUSSED WITH THE MECHANIC ON BOARD; THAT I DIDN'T TRUST THE RELIABILITY OF THE SYSTEM. THE WAY I WROTE UP THE SYSTEM IS AS FOLLOWS: 'TCAS APPEARS TO GIVE ERRONEOUS COMMANDS. TA WHEN THERE IS NO TFC; RA TO CLB WHEN TFC ABOVE VISUAL.' THE NEXT DAY WAS INTERESTING; TOO. THE FAS COULD NOT HEAR US ON THE INTERPHONE WHEN WE TRIED TO COMMUNICATE WITH THEM. AURAL WARNING CIRCUIT BREAKER TRIPPED MULTIPLE TIMES WHICH PREVENTED THE AUTOPLT DISCONNECT WARNING. FURTHERMORE; THE AUTOPLT ITSELF; DISCONNECTED MORE THAN A FEW TIMES UNCOMMANDED; OF COURSE WITH THE AURAL WARNING BREAKER TRIPPED; TWICE WE HAD NO AUDIBLE WARNING; AND A COUPLE OF TIMES WE DID; WHEN BREAKER WAS NOT TRIPPED. I BROUGHT THIS TO MECHANICS ATTENTION AS WELL. MULTIPLE TIMES ON MULTIPLE LEGS OF THIS CHARTER; WE EXPERIENCED AUTOPLT SIMPLY IGNORING LNAV ENGAGEMENT; AND TURNING OFF COURSE BY ITSELF. SEVERAL TIMES WE NOTED FLT DIRECTOR GIVE ERRONEOUS COMMANDS TO PITCH DOWN WHEN REALLY NOT NEEDED. A FEW TIMES WE HAD TO SIMPLY TURN FLT DIRECTORS OFF; AND HAND FLY THE ACFT DUE TO UNRELIABILITY OF THE SYSTEM. MECHANIC WAS A WITNESS TO THIS ON AT LEAST TWO OCCASIONS THAT I RECALL; AND I REMEMBER DISCUSSING THE ISSUE WITH HIM. XPONDER IRREGULARITIES SEEMED TO OCCUR ON JUST ABOUT EVERY LEG; I.E. CTLRS INFORMED US OF LOSS OF MODE C; AND ASKED US TO RESET XPONDER NUMEROUS TIMES OVER THE COURSE OF THIS CHARTER. I DO NOT REMEMBER THE EXACT FLT NUMBER; BUT ON ONE OCCASION THE ATC CTLR QUERIED; 'SAY ALT.' WHEN WE TOLD HIM WE WERE LEVEL AT FL330; HE STATED; 'CHECK ALTIMETER 29.92'; WHICH WE VERIFIED WITH HIM THAT ALTIMETER WAS APPROPRIATELY SET. FO TURNED THE SELECTOR TO THE #2 XPONDER; AND CYCLED THE XPONDER MODE SELECTOR TO STBY THEN BACK TO TA/RA. THE CTLR STATED THAT HE WAS THEN RECEIVING. I ASKED HIM IF THAT XPONDER LOOKED BETTER; AND HE SAID 'YES; I SHOW YOU AT LEVEL AT FL330; BUT BEFORE IT WAS ALMOST 300 FT OFF.' NOW BY THIS POINT; I AM VERY IRRITATED BY THE FACT THAT THESE ANOMALIES ARE BY THEMSELVES BENIGN; BUT IN THE INTEREST OF SAFETY; WHEN THE COMBINATION OF SAME START COMPILING; IT BECOMES DISCONCERTING THAT THINGS JUST SHOULD NOT BE ACTING THIS WAY. I DISCUSSED THIS WITH THE MECHANIC; AND HE AGREED. AS THE MECHANIC AND I WERE RECOUNTING THE MULTIPLE ELECTRICAL ABNORMALITIES; I ASKED HIM; 'WHAT COULD POSSIBLY BE CAUSING THIS?' HE REPLIED; 'MOISTURE.' DURING THIS DISCUSSION; MY FO COMMENTED THAT DURING THE PREFLT WALK AROUND INSPECTION; HE WITNESSED WATER RUN OUT ONTO THE GROUND WHEN HE OPENED THE E&E BAY HATCH. MECHANIC SAID THAT HE ASSUMED AT THE TIME; THAT IT WAS MERELY RAINWATER TRAPPED AROUND THE HATCH SEAL. MAINT INFORMED ME THAT THE AIRSTAIR DOOR WAS PROBABLY HOW HEAVY RAIN; PRIOR TO OUR FLT; ENTERED THE ACFT AND GOT DOWN INTO THE E&E BAY. I RECALL THAT AFTER OUR DISCUSSION AND UPON REACHING ONE OF OUR DESTINATIONS; HE TOLD ME THAT HE WAS GOING TO TRY TO RESET SOME THINGS IN THE E&E BAY. ONCE BACK IN THE AIR AGAIN; WE WERE SOMEWHERE ENRTE AT CRUISE ALT; WHEN WE RECEIVED ANOTHER TA DEPICTING TFC 5 MILES AHEAD OUR ALT. JUST LIKE BEFORE; WE ASKED ATC ABOUT IT; AND JUST LIKE BEFORE; THE 'TFC' JUST DISAPPEARED FROM THE DISPLAY. ATC SHOWED NO TFC ON HIS RADAR AT OUR ALT OR EVEN IN OUR VICINITY! ON ONE OF THE LEGS; UPON APCH TO LNDG; MY LOC INDICATIONS FAILED. I TRANSFERRED THE VHF NAV SWITCH TO 'BOTH ON 2.' THIS GOT ME A DISPLAY BACK; AND IT APPEARED TO WORK FINE. ON THE NEXT; AND FINAL LEG THAT DAY; THE SAME THING OCCURRED AGAIN. I MADE THE DECISION TO WRITE IT UP; ASWELL AS THE MATTER OF THE AUTOPLT DISCONNECTING. THE MECHANIC REMAINED AT THE ACFT TO TRY AND RESOLVE THESE ISSUES. LATER HE INFORMED ME THAT THE ACFT WOULD BE READY TO GO THE NEXT AFTERNOON. MECHANIC LATER TOLD ME THAT HE HAD TO SWAP AURAL WARN CIRCUIT BREAKER WITH A NON-CRITICAL ONE; I.E. AN OVERHEAD LIGHTING CIRCUIT BREAKER. THE THIRD AND FINAL DAY OF THE ADVENTURE WAS A LITTLE BETTER; WITH THE EXCEPTION OF THE AUTOPLT REFUSING TO ENGAGE ON THE FIRST; SECOND AND THIRD ATTEMPT FROM THE FO. ALSO THE PREVIOUSLY MENTIONED XPONDER ISSUES WERE NOT AS FREQUENT. I ONLY RECALL ATC TELLING US THAT RADAR CONTACT WAS LOST; ONCE ON THE LAST DAY; AND AGAIN THIS OCCURRED DURING CRUISE FLT. BECAUSE I AM NOT A MECHANIC; I WILL NOT PRESUME TO SAY WITH ANY CERTAINTY THAT 'MOISTURE' WAS DEFINITELY THE AFFECTING FACTOR; BUT IT DOES NOT SEEM THAT OVER TIME THE PROBS BECAME FEWER AND FEWER. PERHAPS THE ACFT IS 'DRYING OUT.' CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE AIRPLANE WAS PARKED OUTSIDE IN HEAVY DRIVING RAIN WITH THE AIRSTAIRS RETRACTED; BUT WITH THE AIRSTAIR DOOR LEFT OPEN ALLOWING WATER TO ENTER THE ELECTRICAL AND ELECTRONIC COMPARTMENT. THE RPTR SAID TROUBLES STARTED ON TAXI OUT THE FIRST DAY WITH CALL CHIME AND INTERPHONE PROBS AND CONTINUED THROUGHOUT THE DAY WITH FALSE TCAS TARGETS AND ERRONEOUS COMMANDS CAUSING LOSS OF SEPARATION. THE RPTR STATED AUTOPLT; FLT DIRECTOR PROBS AND XPONDER MODE 'C' ERRORS BEING XMITTED CONTINUED DURING THE THREE LEGS.