ACFT EQUIP PROBLEM EXACERBATES ENRTE WX AND ICING ENCOUNTER.

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IN PLANNING A FLT FROM ALLEGHENY COUNTY; PA; TO CENTRAL NEW JERSEY; I RECEIVED WX INFO FROM AN ACR WX SVC AT AGC. MY PRIMARY CONCERN WAS ICING CONDITIONS; WHICH WERE FORECAST AS MODERATE TO OCCASIONALLY SEVERE ALONG THE FIRST PORTION OF MY RTE. VARIOUS RPTS OF ICING FROM TRACE TO MODERATE (AS I RECALL) APPEARED IN PIREPS. I SHOULD HAVE GONE TO A HOTEL RIGHT THEN. UNFORTUNATELY; I HAD A BAD CASE OF GET-HOME-ITIS AND CONVINCED MYSELF THAT IT WOULD BE REASONABLE TO JUST 'CHK THINGS OUT' AND RETURN TO AGC IF I ENCOUNTERED ANY ICING. (AGC HAD BEEN MVFR EARLIER THAT DAY; BUT HAD JUST GONE IFR WITH AN 800 FT CEILING). BOLSTERING THIS FOOLISH THOUGHT WAS A RPT FROM A PLT WHO HAD RECENTLY ARRIVED FROM THAT DIRECTION AND SAID THAT HE HAD BEEN ON TOP AT 6000 AND ENCOUNTERED NO ICING. IN ADDITION; THERE WERE ALTERNATES CLOSELY SPACED ALONG THE EARLY PORTION OF THE RTE THAT WERE VFR OR NEARLY SO. I PULLED OUT THE APCH PLATES FOR THE ALTERNATES AND STUDIED THEM; ONCE AGAIN CONVINCING MYSELF; STUPIDLY; THAT IT WAS OK TO SET OUT SINCE I HAD 'PLENTY' OF OPTIONS IN CASE ANY ICE WAS ENCOUNTERED. I FILED IFR AT 7000. I PREFLTED THE ACFT CAREFULLY. I ALSO VERIFIED THAT MY GEAR WAS LOCKED DOWN CORRECTLY; SINCE ON THE PREVIOUS LEG OF MY FLT; I HAD HAD A PROBLEM WITH THE GEAR MOTOR AND HAD EXTENDED IT MANUALLY. THE MECHANISM WAS LOCKED OVER-CTR AS IT SHOULD BE. (IT WAS A HOLIDAY WKEND; AND NO MECHS WERE AVAILABLE AT AGC THAT DAY TO RESET IT). I AGAIN REVIEWED THE APCH PLATE FOR AGC AND THE APCHS FOR LATROBE AND JOHNSTOWN; IN CASE I HIT ICE AND HAD TO RETURN OR DIVERT. I TURNED ON THE HEAT AND DEFROST FULL BLAST; AND VERIFIED THEIR OP. ONCE AGAIN; THIS 'THINKING AHEAD' ADDED TO THE ILLUSION OF APPROPRIATELY-MANAGED RISK. ON THE RUNUP PAD; I TOLD THE LCL CTLR THAT I WAS JUST GOING TO 'TAKE A LOOK' AND WOULD RETURN TO AGC IF I HAD ANY PROBLEMS. HE SAID HE WOULD PASS THAT INFO ALONG TO THE APCH CTLR. MY INITIAL CLRNC WAS TO 3000; WITH EXPECTATION OF 7000 IN 10 MINS; ACCORDING TO THE SID. I WAS CONCERNED ABOUT THIS; SO I ASKED IF HE COULD CHK WITH APCH ON THE POSSIBILITY OF GETTING AN IMMEDIATE CLB TO MY FINAL ALT. HE CHKED; AND THE ANSWER WAS THAT I COULD EXPECT A CLB WITHOUT DELAY. HERE AGAIN; BOTH OF THESE THINGS ADDED TO THE FEELING THAT I WAS THINKING AHEAD; PREPARING RATIONAL ALTERNATIVES IN CASE OF AN ICING ENCOUNTER. IT'S SURPRISING HOW YOU CAN FOOL YOURSELF SOMETIMES. I DEPARTED AND WAS CLRED IMMEDIATELY TO 7000 AS PROMISED. APCH SAID THAT ANOTHER ACFT WAS ON TOP AT 5800. I REACHED 6000; AND WAS NOT ON TOP YET; BUT HAD ENCOUNTERED NO ICE. HOWEVER; I WAS CLBING MORE SLOWLY THAN USUAL; BECAUSE OF MY EXTENDED LNDG GEAR; AND A SHORT TIME LATER; AT AROUND 6500 FT; I STARTED TO GET A TRACE OF ICE ON THE WINDSHIELD. I ASKED THE CTLR IF 6000 WAS OK FOR A WHILE; AND HE CLRED ME BACK DOWN TO 6000. NO MORE ICE ACCUMULATED; HOWEVER; WITH NO GUARANTEE THAT 6000 WOULD STAY ICE-FREE AND WITH KNOWN ICE ABOVE; I TOLD APCH THAT I'D LIKE TO DIVERT TO EITHER JOHNSTOWN OR LATROBE; BOTH OF WHICH WERE CLOSE BY. HE SUGGESTED LATROBE; AND VECTORED ME ONTO THE LOC; CLRED ME FOR THE APCH; AND I LANDED WITHOUT INCIDENT. DURING THE DSCNT; ICE BEGAN TO ACCUMULATE RAPIDLY. BY THE TIME I LANDED; I HAD ABOUT A 6 INCH ICE FREE SPOT IN THE WINDSHIELD TO LOOK THROUGH AND THE AIRPLANE HAD ABOUT 1/2 INCH OF ICE ON ALL THE LEADING SURFACES. IF I HAD HAD TO GAR FOR ONE REASON OR ANOTHER OR HAD TO SPEND MUCH MORE TIME IN THOSE DSCNT CONDITIONS; I MIGHT NOT HAVE MADE IT. WHEN I GOT BACK TO MY HOTEL ROOM I JUST COULDN'T BELIEVE THAT I HAD; IN A VERY REAL SENSE; RISKED MY LIFE JUST TO GET HOME A DAY EARLIER. CONTRIBUTING HUMAN FACTORS: STRONG DESIRE TO GET SOMEWHERE; OVERCONFIDENCE DUE TO PRESENCE OF OPTIONS AND WILLINGNESS TO DIVERT; INSUFFICIENT KNOWLEDGE OF AND EXPERIENCE WITH ICING PHENOMENA; POOR JUDGEMENT.