My GE side by side m# GSL25JFAPBS is too warm in freezer compartment, around 32 F.
I took the back cover off and found the lower 3rd of the evaporator coils frosted over and the upper portion with no frost (see pic). I ohmed the defrost heater and found 21 ohms, assume it is good. I checked the defrost thermostat and it stayed closed during testing in a cup of ice and blowing a hair dryer over it out of circuit, so I assumed it is bad. The evaporator fan is blowing well. I got a new thermostat today and installed it but after about 3hrs the symptoms are the same. Could use some advise on what to do next.

Thanks

Here your parts. I think the "AP" in the model number should be PA.
Replacement parts for GSL25JFAPBS models | AppliancePartsPros.com

Looks like you may have a low freon problem.
http://www.applianceaid.com/frig_notcold.html
Take a look at the example pictures in the 5th paragraph.

I would check that the condenser/compressor fan is running and that the condenser coils are clean.

If low freon is the case then the repair will be expensive as you will need a pro.
Finding and repairing a leak can be time consuming. Also there is no guarantee of a long term fix.
In most cases it makes more sense to put those dollars towards a new unit.

Check the purchase date as the sealed system should have a 5 year warranty,