A DHC6 FLC ON FERRY FLT FROM ANC TO YAK DISCOVERS THAT THE PLT'S DIRECTIONAL GYRO AND ADF ARE NOT IN AGREEMENT WITH OPPOSITE SIDE DURING AN NDB APCH.

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WHILE PREFLTING THE ACFT; A WIRE HARNESS WAS FOUND HANGING LOOSE AND INTERFERING WITH THE RUDDER PEDAL MOVEMENT. I INQUIRED WITH MAINT; THEY INVESTIGATED AND RECONNECTED. THEY SAID IT WAS THE WIRE HARNESS FOR THE CAPT'S ADF. WE DEPARTED ON A PART 91 IFR FLT ANC-YAK CONDUCTED ON A FERRY PERMIT. I DECIDED TO DIVERT TO CDV FOR FUEL DUE TO YAK WX. I MADE MY REQUEST WITH ZAN AND WAS CLRED TO CDV VIA THE JOH/HBK TRANSITION; CLRED FOR THE NDB; MAINTAIN 6000 FT UNTIL ESTABLISHED ON PUBLISHED PORTION. I STARTED DSCNT; BRIEFED THE APCH WITH THE FO; AND HAD NOTED THAT A LARGE AMOUNT OF L CRAB WAS NEEDED TO HOLD OUR COURSE. I CROSSED THE HBK AND CONTINUED DSCNT TO 1500 FT AND TURNED R TO 105 DEGS. ALL OPS SEEMED NORMAL TO THIS POINT. I TUNED THE CAPT'S ADF TO GCR AND REQUESTED THE FO TO IDENT AND MONITOR THE GCR. HE SAID HE DID BUT IT WAS WEAK. I STARTED TO PICK UP GND REF. OUR INSTS DIDN'T SEEM CORRECT IN REF TO THE GND. I REQUESTED THE FO TO TUNE AND IDENT THE GCR NDB ON THE #2 ADF. HE DID SO; GOT A GOOD IDENT AND THE NEEDLES HAD A 10 DEG SPLIT; HOWEVER; I BELIEVED HIS ADF TO BE RELIABLE. THE #2 ADF REPRESENTED THAT WE WERE ON THE 182 DEG BEARING FROM GCR. I TURNED TO A HDG OF 330 DEGS TO REINTERCEPT THE 195 DEG BEARING FROM GCR. I DSNDED TO 1000 FT AND HAD GOOD VISUAL REF TO EGG ISLAND; HAWKINS ISLAND; HOOK POINT; EYAK GAP; ALTHOUGH I COULDN'T SEE THE ARPT FOR A VISUAL. AT THAT TIME JNU FSS CONTACTED US AND REQUESTED OUR POS AND RELAYED TO THE FO TO TELL THEM WE WERE INBOUND TO EYAKS INTXN. AT THAT TIME THE DME REPRESENTED US TO BE 18 DME FROM CDV. JNU FSS REQUESTED OUR ALT; THE FO RESPONDED 1000 FT. JNU FSS RESPONDED THAT ZAN SHOWED US HEADED BACK TOWARDS HBK. JNU FSS THEN AMENDED OUR CLRNC TO MAINTAIN 1500 FT UNTIL ESTABLISHED ON A PUBLISHED PORTION CLRED FOR THE NDB-A APCH TO CDV. I DECIDED THAT DUE TO THE UNRELIABILITY OF THE INSTS AND KNOWN BUT OBVIOUSLY INCORRECT GEOGRAPHICAL POS THAT THE APCH SHOULD BE DISCONTINUED. I DIDN'T FEEL I COULD RELIABLY IDENT EYAKS INTXN; SO I MADE A TURN TO THE E; KNOWING THAT IT WOULD AT LEAST PROVIDE TERRAIN CLRNC. I CONTACTED JNU FSS AND REQUESTED THE ILS RWY 27 CDV. JNU FSS RESPONDED THAT RADAR WAS INTERMITTENT IN THAT AREA AND ASKED IF I COULD MAINTAIN MY OWN TERRAIN AND OBSTACLE CLRNC WITH SUITABLE NAV TO PROCEED TO THE GCR NDB FOR THE TRANSITION TO THE RWY 27 ILS. I FELT I COULD COMPLY AND STATED SO TO JNU FSS. I WAS INSTRUCTED TO CLB TO 5300 FT AND PROCEED DIRECT TO THE GCR NDB FOR THE TRANSITION TO THE ILS RWY 27 CDV. IN THE CLB; I GOT CLR VISUAL ON THE CDV ARPT; I CANCELED IFR. UPON LINING UP ON FINAL FOR RWY 9; I DISCOVERED THAT BOTH THE FO'S AND CAPT'S RMI'S AND THE CAPT'S HSI REPRESENTED 043 DEGS INSTEAD OF 090 DEGS. FACTORS: 1) SUSPECTED THE #1 ADF TO BE UNRELIABLE. 2) DIRECTIONAL GYRO HAD A FAULTY SLAVE SWITCH WHICH ALLOWS THE COMPASSES TO PRECESS. FOUND THE SWITCH TO BE DIRTY AND WOULD NOT STAY IN THE 'SLAVE IN' POS. 3) NONSTANDARD INST PANELS IN COMPANY ACFT. A) 1 DIRECTIONAL GYRO SYS VERSUS 2 INDEPENDENT SYS. B) NONSTANDARD AUDIO PANELS. CAPT'S ADF COULD NOT BE IDENTED BY THE FO. THIS IS DIFFERENT FROM OTHER COMPANY ACFT. BUT DUE TO BLEED OVER; THE WEAK IDENT WAS HIS OWN ADF. 4) MAGNETIC COMPASS IS UNRELIABLE WHEN WINDSHIELD HEAT IS USED. 5) FO HAD 13 HRS IN TYPE AND IT WAS HIS FIRST FLT IN THAT ACFT. 300 HRS TOTAL. MISTAKE: DELAYED DISCONTINUING OF THE APCH.