Drip pan on frig over flowing and coil on back of frig is freezing up this is an old whirlpool model can any one give idea of what the problem can be.

The defrost timer switch needs changed out.

Sorry Twink, got to disagree. If fridge were not going into defrost there would be no water in evaporator pan. If stuck in defrost mode, coils would not be frosting up.

Stackhouse.
Check interior air circulating fan, check to insure that nothing blocking air ducts or openings between freezer and refrigerator compartments.