Panasonic NN-ST342M Service Manual page 27

(TROUBLE 6) Oven does not cook properly when programmed for the set power level
(Operates properly on HIGH)
CONDITION
Output is full when
you set lower
power level.
CHECK
Disconnect the
wire leads from
relay 2 and check
continuity relay 2.
(Operate the unit)
RESULT
Abnormal.
5-17
CAUSE
Defective P.C.B.
assembly.
REMEDY
Replace P.C.B.
assembly.