MLT WITH FAULTY VOR BROKE OUT 1 NM LEFT OF CENTER LINE ON A VOR APCH TO OQU. ACFT CONTINUED 2 MORE FLTS BEFORE THE FLT CREW RECOGNIZED THE PROBLEM.

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CLRED VOR RWY 34 APCH. THE PNF CONTACTED QUONSET TWR AT THE FINAL APCH FIX. TWR STATED THAT APCH CTL ADVISED THAT WE WERE ABOUT 1/4 MI LEFT OF COURSE. WE VERIFIED OUR INSTRUMENT INDICATIONS; WHICH SHOWED AT MOST 1/2 DEG LEFT OF COURSE. I IMMEDIATELY INCREASED MY WIND CORRECTION AND REGAINED CENTERLINE. WE CONTINUED THE APCH AND BROKE OUT OF IMC CONDITIONS AT 700' MSL. WE WERE APPROX 1 MI LEFT OF COURSE; WITH THE COURSE DEVIATION INDICATOR STILL CENTERED ON COURSE. TWR ISSUED A LOW ALT ALERT AS WE MANEUVERED FOR LNDG AND WE ACKNOWLEDGED THAT WE WERE VMC WITH THE RWY IN SIGHT. AFTER LNDG; TWR STATED THAT APCH CTL WANTED TO KNOW IF WE EVER WERE ESTABLISHED ON FINAL APCH COURSE. WE REPLIED IN THE AFFIRMATIVE. WE DEPARTED FOR ANDREWS AFB (NSF). PRIOR TO TAKING THE RWY WE ASKED TWR IF ANYONE ELSE USING THE VOR APCH HAD EXPERIENCED ANY PROBS. TWR STATED THAT WE WERE THE ONLY ACFT TO HAVE ANY PROBS AND WE SHOULD HAVE OUR EQUIP CHKED. WE XCHKED OUR VOR-1 INFO WITH THE TACAN AND DID NOT SHOW ANY APPRECIABLE DIFFERENCE. ON OUR FINAL LEG FROM ANDREWS AFB (NSF) TO SELFRIDGE ANGB (MTL) WE WERE ASKED BY WASHINGTON (POSSIBLY CLEVELAND) CENTER IF WE SHOWED OURSELVES ON COURSE. WE REPLIED THAT WE DID AND CENTER REQUESTED OUR HDG. AFTER WE RESPONDED THEY STATED THAT WE WERE 7 MI OFF COURSE. WE WERE THEN ISSUED RADAR VECTORS DIRECT WHEN ABLE. WE INFORMED CENTER THAT WE HAD HAD TROUBLE WITH THE VOR-1 RECEIVER. THE VOR-2 AGREED WITH THE POS GIVEN BY CENTER. WE UTILIZED VOR-2 TACAN FOR NAV FOR THE REMAINDER OF THE FLT. I BRIEFED THE APCH TO QUONSET STATE TO THE PNF; BUT FAILED TO RECOGNIZE THAT HE SELECTED VOR-1 INSTEAD OF THE NORMAL VOR-2 FOR HIS COURSE INFO. WITH BOTH OF US ON VOR-1; WE HAD NO XCHK. HAD I RECOGNIZED THIS; WE WOULD HAVE DETERMINED THE VOR-1 TO BE UNRELIABLE AT THE TIME TWR INDICATED THAT WE WERE OFF COURSE. AFTER EXPERIENCING THE PROBS ON FINAL AT QUONSET STATE; WE SHOULD HAVE UTILIZED ONLY TACAN AND VOR-2 FOR THE REMAINING FLTS.