DUE TO NAV RECEIVER PROB; LGT BEGAN DSCNT EARLY.

Narrative

FROM DOWNWIND A VECTOR OF 070 DEGS WAS GIVEN TO INTERCEPT THE ILS FOR RWY 4; CROSS CRENE (11.1 DME) AT 2700 FT OR ABOVE; CLRED APCH. ON APCHING THE LOC; A GS CAPTURE WAS ACCOMPLISHED ON MY FLT DIRECTOR; RAW DATA CONFIRMED ON GS. DSCNT ON GS STARTED AND LOC CAPTURED. FLT DIRECTOR PRESENTATION NORMAL. AT 2000 FT ABOVE GND I ASKED WHAT VOR MY FO HAD ON HIS NAV RECEIVER. HE REPLIED THAT HE HAD LGA VOR TUNED. DME AT THE TIME WAS 13 DME. OBVIOUSLY A CONFLICT. I CLBED TO 2700 FT AFTER SWITCHING MY NAV RECEIVER TO AUX WHICH SHOWED ME FULL DEFLECTION BELOW GS. A NORMAL APCH WAS MADE FROM THAT POINT. CONCLUSION: POOR COCKPIT PROC. GRENE WAS NEVER IDENTED AT THE START OF THE APCH; RESULTING IN THE CAPTURE OF A FALSE GS OR PERHAPS A FAULTY NAV RECEIVER. ACFT WAS 1000 FT LOW OUTSIDE GRENE! APCH CTL NEVER ADVISED US OF OUR ALTDEV. BETTER OBSERVANCE OF PUBLISHED PROCS BY BOTH PLT AND CTLR A MUST. THIS COULD HAVE BEEN A DISASTER! CALLBACK CONVERSATION WITH REPORTER REVEALED THE FOLLOWING: RPTR SAID THAT THERE WAS A PROB WITH THE GS RECEIVER. ON THE NEXT LEG; TO BOS; THE GS 'POPPED IN AND OUT WITH OCCASIONAL FLAGS.' RPTR IS MOST UPSET THAT NOBODY NOTICED THE DEV FOR SO LONG.