A320 HAD TO ABANDON AN APCH WHEN A RED GEAR UNSAFE LIGHT ILLUMINATED. FOLLOWED SOP EXCEPT FOR THE GRAVITY EXTENSION OF THE GEAR. LIGHT REMAINED ON. LNDG WAS NORMAL BUT NOSE GEAR STEERING FAILED WHILE TAXIING.

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ON APCH TO RWY 27L AT ORD GOT A RED WARNING THAT LNDG GEAR WAS UNSAFE. LOWER ECAM SHOWED 1 RED TRIANGLE ON NOSE GEAR. EXECUTED MISSED APCH. ADVISED ATC. RECYCLED LNDG GEAR AND HAD EVERYTHING GREEN UNTIL CONFIGURED FLAPS 3 DEGS FOR ILS; AGAIN GOT CONTINUOUS REPETITIVE CHIME; RED MASTER WARNING. ECAM WARNING GEAR UNSAFE AND RED TRIANGLE ON ECAM NOSE GEAR. I ASSUMED THE PROB WAS BEING CAUSED BY A FAULTY PROX SWITCH BUT COULDN'T BE ABSOLUTELY SURE SO DECLARED AN EMER AND BRIEFED THE FLT ATTENDANTS FOR A POSSIBLE NOSE GEAR FAILURE ON TOUCHDOWN. COMPLETED THE LNDG GEAR DOWN/NOT LOCKED QRH CHKLIST EXCEPT DID NOT DO THE GRAVITY EXTENSION PROC AS CALLED FOR SINCE I WAS PRETTY SURE THE NOSE GEAR WAS DOWNLOCKED. LANDED WITHOUT INCIDENT HOWEVER; NOSEWHEEL STEERING FAILED DURING TAXI AND HAD TO BE TOWED TO GATE. MAINT DETERMINED PROX SWITCH ON NOSE GEAR WAS IN FACT DEFECTIVE. IN RETROSPECT; I SHOULD HAVE COMPLETED THE ENTIRE QRH CHKLIST AS PUBLISHED INCLUDING THE GRAVITY EXTENSION OF THE LNDG GEAR AS HAD THE NOSE GEAR COLLAPSED ON LNDG I MAY HAVE BEEN CRITICIZED; OR WORSE; FOR NOT DOING SO. HENCEFORTH IF I HAVE ANY PROB THAT HAS A QRH CHKLIST; I WILL PERFORM THE CHKLIST IN ITS ENTIRETY TO MAKE SURE ALL BASES ARE COVERED.