A HYPERACTIVE GPWS CAUSES AN ACR MLG TO CLB.

Narrative

WE WERE BEING VECTORED FOR A LOC RWY 27/VISUAL APCH AT SAN. WX ON THE ATIS WAS 3500 FT BROKEN; 10 MI VISIBILITY; WIND 240 DEG AT 8 KTS. WE WERE BEING STEPPED DOWN BY SAN APCH CTL ON A 250 DEG HDG AND CLRED TO 4000 FT MSL. WE WERE THEN CLRED FOR THE APCH AND CLRED TO INTERCEPT THE LOC ON OUR 250 DEG HDG AND CLRED TO 3800 FT MSL UNTIL ESTABLISHED ON THE LOC. ON THIS HDG; IT APPEARED WE WOULD INTERCEPT THE LOC VERY CLOSE TO SWATT/12.6 DME ON LOC. I REMEMBER THINKING THAT WE MIGHT STILL BE AT 3800 FT UNTIL INSIDE SWATT WHERE THE PUBLISHED ALT IS 3600 FT. DSCNT RATE AT THIS TIME WAS APPROX 1000 FPM. PASSING THROUGH 4000 FT WITH FLAPS 15 DEGS AND SLOWING FROM 200 KTS TO 180 KTS; WE RECEIVED A GPWS TERRAIN WARNING. AUTOPLT AND AUTOTHROTTLE WERE DISCONNECTED AND A CLB ESTABLISHED. FO ADVISED APCH WE WERE CLBING DUE TO GPWS TERRAIN WARNING AND RESPONSE FROM APCH WAS THAT MVA IN OUR AREA WAS 3800 FT MSL. AT THIS TIME WE COULD SEE GND TO THE L AND R OF ACFT; BUT NOT IMMEDIATELY BENEATH OR IN FRONT DUE TO CLOUDS. WE CLBED PROBABLY 400-500 FT UNTIL WE BROKE OUT OF CLOUDS AND COULD SAFELY SEE IN FRONT OF US. ABOUT THIS TIME WE ALSO INTERCEPTED THE LOC AND WERE ABLE TO CONTINUE THE APCH. WE WERE CLRED TO TWR FREQ AND CONTINUED AND LANDED NORMALLY.