PLT OF BE36TC HAS PROB WITH SUCTION COMPROMISING THE USE OF THE DIRECTIONAL GYRO. HE DIVERTS TO NEARBY ARPT WITH VECTORS FROM APCH CTLR.

Narrative

I DEPARTED WEST HOUSTON ARPT FOR NASHVILLE. I HAD 1 PAX ON THE TRIP. I WAS FLYING MY PLANE; A BONANZA B36TC ACFT. I FILED IFR AND RECEIVED MY CLRNC AND DEPARTED. I WAS CLRED VIA VECTORS TO LFK WITH AN INITIAL ALT OF 2000 FT AND HDG OF 270 DEGS. I WAS TOLD TO EXPECT 11000 FT; 10 MINS AFTER DEP. THERE WAS AN OVCST CEILING AT 1000 FT. I ESTIMATED THE TOP TO BE 3500 FT. I WAS CLRED TO 3000 FT APPROX 5 MINS AFTER DEP AND AS I RECALL; WAS GIVEN NEW HDGS OF INITIALLY 300 DEGS AND THEN WITHIN A COUPLE OF MINS; 360 DEGS. I LOOKED TO SEE WHAT MY SUCTION GAUGE WAS SHOWING. IT WAS NOT IN THE GREEN; WHICH IS 4.3 TO 5.9; BUT RATHER WAS AT 2.0. AS I HAD ONLY THE DAY BEFORE HAD THE A&P MAINT SHOP INSTALL A NEW SUCTION GAUGE IN ORDER TO MAKE ROOM FOR A NEW ENG CYLINDER MONITOR; I BECAME CONCERNED AS TO WHETHER MY DIRECTIONAL GYRO WAS WORKING CORRECTLY GIVEN THAT IT IS A PRESSURE INST. MY VERT SPD INST AND ARTIFICIAL HORIZON APPEARED TO BE WORKING CORRECTLY; WHICH ARE ALSO PRESSURE INSTS. I INFORMED ZHU THAT MY SUCTION GAUGE (PRESSURE SYS) APPEARED TO BE INOP AND THAT I WANTED TO CHANGE MY FLT PLAN AND RETURN TO SGR. I REQUESTED SGR AS THEY HAVE AN ILS APCH WHERE IWS ONLY HAS AN NDB AND VOR APCH AND WITH THE WX CONDITIONS DETERIORATING; I THOUGHT SGR WOULD BE MORE PRUDENT. ZHU ASKED IF I WAS DECLARING AN EMER. I CAN'T REMEMBER MY SPECIFIC RESPONSE OTHER THAN MY COMMUNICATING AGAIN THE NATURE OF MY PROB AND MY DESIRE TO RETURN TO SGR. DURING THIS TIME AND THROUGHOUT THE FLT I WAS IN THE CLOUDS. ZHU ADVISED ME THAT DWH WAS CLOSER THAN SGR AND ASKED IF THAT WAS OK. BECAUSE OF MY CONCERN AS TO THE DIRECTIONAL GYRO AND GIVEN MY DIFFICULTY IN FOCUSING SOLELY ON THE MAGNETIC COMPASS FOR DIRECTIONAL NAV WHILE IN THE CLOUDS AND LIGHT TURB; I REQUESTED RADAR VECTORS TO THE FINAL APCH COURSE TO THE LOC RWY 17R APCH AT DWH. ZHU OBLIGED AND PROVIDED ME DIRECTIONAL GUIDANCE AS WELL AS DSNDING ALT CLRNCS DURING THIS PERIOD OF TIME. ZHU ALSO ASKED IF I REQUIRED EMER EQUIP AT DWH AND I ADVISED THEM I DID NOT. WHEN I BROKE OUT OF THE CLOUDS ON APPROX A 2 MI FINAL; I ADVISED ZHU THAT I HAD THE ARPT IN SIGHT AND WAS INSTRUCTED TO SWITCH TO THE FREQ OF THE DWH CTLR AND THAT I WAS CLRED TO LAND. THE DWH CTLR CLRED ME TO LAND AND THEN PROVIDED ME TAXI INSTRUCTIONS INCLUDING TAXI BACK ON RWY 17R AND THEN TO THE RAMP AND PARKING AREA. THEY DID NOT REQUEST THAT I CALL ANYONE IN RESPECT TO THE CIRCUMSTANCES WHICH NECESSITATED MY LNDG AT DWH. I AM SUBMITTING THIS RPT OUT OF CONCERN AS TO WHETHER ATC CONSIDERED MY ACTIONS TO HAVE BEEN A DECLARED EMER AND AS SUCH THE POSSIBILITY THAT I AM REQUIRED TO SUBMIT A RPT OR CONTACT THE FAA OR A NTSB FIELD OFFICE.