PLT OF A TWIN ENG RECIPROCAL ACFT TURNS ON PITOT HEAT; STALL WARNING HEAT AND PROP HEAT PRIOR TO TKOF. AT ABOUT 1000 FT THE AIRSPD GOES TO ZERO BUT THE VSI AND ALTIMETER SHOW A CLB. TRYING TO SOLVE THE PROB; RPTR LEVELS OFF AT ASSIGNED ALT; HE IS CONTACTED BY ATC; AND QUERIED ABOUT HIS ALT. HE IS AT 13700 FT VERSUS 12000 FT. HE DISCOVERED THE ALTERNATE STATIC SOURCE HAD BEEN TURNED TO HALF OPEN. PROB SOLVED.

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I LINED UP ON THE RWY CTRLINE AND TURNED ON THE PITOT HEAT STALL WARNING HEAT; PROP HEAT; AND TURNED THE XPONDER TO ALT. ON THE TKOF ROLL; ALL THE ENG INSTS WERE IN THE GREEN FOR BOTH ENGS. THE AIRSPD WAS INCREASING AND I ROTATED A FEW KTS ABOVE VMC. AFTER CLBING ABOUT 1000 FT; THE PLT'S AIRSPD WENT TO ZERO. THE VSI SHOWED A CLB OF 500 FPM AND THE ALTIMETER WAS SHOWING A CLB ALSO. I THOUGHT I HAD A PITOT PROB AND WAITED TO SEE IF THE PITOT HEAT WOULD FIX THE PROB. I CLICKED THE PITOT HEAT OFF AND ON TO SEE IF IT WAS WORKING AND IT SHOWED AN INCREASE IN AMPERAGE; WHEN TURNED ON; ON THE ALTERNATOR AMMETER. I ALSO CHKED THE COPLT'S AIRSPD INDICATOR AND IT WAS FUNCTIONING OK. I DIDN'T INFORM ATC RIGHT AWAY BECAUSE I HAD THE COPLT AIRSPD INDICATOR AND THOUGHT I'D GIVE THE PITOT HEAT A CHANCE TO WORK LONGER. WHEN I WAS VMC ABOVE THE CLOUDS; I REACHED MY ASSIGNED ALT OF 12000 FT AND BEGAN TO LEVEL OFF. AS I LEVELED OFF; THE VSI AND ALTIMETER STILL SHOWED A CLB. I POINTED THE NOSE DOWN AND THE VSI AND ALTIMETER STILL SHOWED A CLB. AT THIS POINT I LET ATC KNOW I HAD A PROB AND THEY ALSO QUERIED ME AS TO WHAT ALT I WAS CLBING TO. I THEN REFED THE COPLT'S ALTIMETER AND VSI. I WAS THEN AT 13700 FT AND IN A SLOW DSCNT. USING THE COPLT'S VSI AND ALTIMETER I DSNDED BACK TO 12000 FT. WHEN I LEVELED AT 12000 FT THE PLT'S AIRSPD INDICATOR BEGAN WORKING; BUT SHOWED 10 KTS LESS THAN THE COPLT'S AIRSPD INDICATOR. THE PLT'S VSI THEN BEGAN TO SHOW A 500 FPM DSCNT UNTIL THE ALTIMETER REACHED 11800 FT. ALSO; AT ONE POINT DURING THE CLB; BEFORE THE STATIC PROB WAS DISCOVERED; THE PLT'S AIRSPD INDICATOR INCREASED TO 90 KIAS BEFORE DROPPING BACK TO ZERO. I SOON DISCOVERED THE ALTERNATE STATIC SOURCE VALVE HAD BEEN TURNED TO 1/2 OPEN. WHEN I CLOSED THE ALTERNATE STATIC SOURCE VALVE THE PLT'S ALTIMETER JUMPED TO 12000 FT AND THE AIRSPD INDICATOR'S SPDS MATCHED. SOME TIME DURING THE CLB MY L LEG MUST HAVE BUMPED THE ALTERNATE STATIC SOURCE TO 1/2 OPEN AND THAT IS WHEN THE PLT'S AIRSPD INDICATOR DROPPED TO ZERO AND THE VSI INDICATED THE CABIN CLB RATE. TO PREVENT THE RECURRENCE; I WOULD XCHK THE COPLT'S PITOT STATIC INSTS SOONER. I WOULD ALSO LET ATC KNOW ABOUT THE PROB I THOUGHT I HAD SOONER THAN I DID.