Piper ARCHER II Pilot Operating Handbook page 63

If roughness persists, prepare for a precautionary landing at pilot's
discretion.
NOTE
Partial carburetor heat may be worse than no
heat at all, since it may melt part of the ice,
which will refreeze in the intake system. When
using carburetor heat, therefore, always use full
heat, and when ice is removed return the
control to the full cold position.
ISSUED: JANUARY 14, 1981 REPORT: VB-1120
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