Remove eyes or bad spots from potatoes and chop into bite size chunks and boil in salt water until they are cooked but not mushy.
drain water and put potatoes into a bowl and put them in the freezer.
while potatoes are in freezer dice onion and set aside.
in a bowl mix together the mayo pickle relish, mustard and celery seed until combined
when potatoes have cooled in the freezer about 15 minutes mix onions in with the potatoes and then pour mayo mixture over potatoes and onions. Combine well enough that your potatoes are covered.