Hi @gena74261
Leaving the door open for 5 hours would have allowed a lot more warmer moist air to enter the freezer than what would have during normal usage and this could have increased the ice buildup on the evaporator unit to a point where it is blocking the vent and that the defrost cycle cannot defrost it adequately, so more ice continues to build as it cannot all be defrosted during one defrost cycle anymore, as is usually the case.
Initially you would have to turn off the freezer and allow all the ice to melt naturally and then you can check if everything is OK after that or if there a problem with the defrost cycle in the freezer.
I realize that turning the freezer off to melt the ice etc may not only be inconvenient but creates problems as to where to keep all the frozen food etc but defrosting the evap unit can't be done while the freezer is still turned on
You can use a hair dryer to speed up the melting process, but only use it on the coolest setting and only for short periods at a time as you don't want to cause any damage to the evaporator unit. The evap unit is only thin aluminium and is designed to function at below freezing temperatures i.e. 2°F to 8°F
Here's a link that has a video that shows how to replace the evaporator fan in your freezer that may help, at least how to gain access to the evaporator unit etc.
Once all the ice has melted, check that the drain hole beneath the evap unit leading to the evap pan underneath the compartment near the compressor motor is not blocked, preventing the meltwater from reaching the pan. Perhaps pour a cup of water down the drain hole and make sure that it all reaches the pan underneath.
Once the evap unit is free from ice reassemble everything and then turn the freezer on.
It may take a while to reach the correct operating temp but once it does check if everything is OK. With your model the defrost cycle occurs once every 12 hours of compressor run time¹ and lasts for 30 minutes. During this time the compressor and evap fan are turned off and the defrost heater is turned on to melt any accumulated ice off the evap unit. At the end of 30 minutes the heater is turned off and the compressor and evap fan are both turned on again to drive the temps back down again to the set operating temp.
If the ice builds up again as before i.e. noticeable problem then the defrost components would need to be checked to make sure that they're OK i.e. defrost heater, defrost thermostat and defrost timer.
¹ Compressor run time is the accumulated hours that the compressor has been running. During normal operation, the compressor and evap fan will be turned off when the temp in the compartment reaches the set operating temp (2°F). When the temp rises above the preset upper limit (8°F) then the compressor and evap fan will be turned on again to drive the temp back down again. Basically the compressor and fan are turning on and off to keep the temp within the prescribed limits. During the night the compressor may not be operating for long periods of time as the door will not be opened as much or not at all as it is during the day thereby not much cold air will be lost, so it may take more than a day or so to accumulate the 12 hours of running time before the defrost cycle is started
11 
366 
1,4k 