What was found
PILOT REPORTED ALTIMETER HANG-UP AT 5,000 FEET. TESTED IN SHOP, UNIT STOPPED AT 12,000 FEET ON DESCENT. IT WOULD START AT 10,500 FEET. UPON DISASSEMBLY, INSPECTED INSHAKE ON ALL PIVOTS. THERE WAS NO INSHAKE AT ALL. THIS UNIT WAS MFG IN 1979 AND WAS NEVER OVERHAULED SINCE.