inconsistent compressor and condensor fan operation

Compressor start relay would cycle several times before compressor would come on. Replaced start relay and defrost timer assy. Operated more consistently however not completely reliable. Ice would begin to melt. Noticed that if you would cycle the temperature control the compressor would start again and operate for several hours then not cycle again. Jumpered temp control and operation was continuous and reliable. Replaced cold control thermostat. Operation now normal. Suspect high resistance in switch caused start relay and timer contacts to arc. Small amount of carbon noticed under temp control...