My Whirlpool Upright Freezer allows ice to build up on the inside bottom of the freezer. I've defrosted manually and cleaned the drain hose enough times to know that the drain hose is not clogged by anything other than the ice build-up.

My online reading shows possible problems with the defrost timer or defrost termination thermostat. One post shows a drain tupe heater add-on.

The freezer is working very well, except for the blocking of the drain hose with ice and then filling the bottom of the freezer with ice.

What do you suggest to fix it?

Thanks, Ira