Frigidaire window unit problems

Hi, new here. I guess I'll jump right in with my question. We have a Frigidaire model FAS184N2A that has recently started having problems. We generally run the a/c in the afternoon (around 2pm) till bedtime (around 12am) and it has never had a problem cooling the room down to around the same temperature that the thermostat on the unit is set to (usually around 77F) even on very hot days. Recently, though, it has not been cooling the room below around 81 degrees no matter what I have the thermostat on the unit set to. The air coming out is cold (though I really can't tell if it is cold as it should be). The condenser and evaporator seem reasonably clean and it doesn't seem like the air is restricted.

I timed the compressor cycle and it seems that no matter the time of day, or outdoor or indoor temps, or what the thermostat on the unit is set for, the compressor was almost always on five minutes and off three minutes. No matter what, it seems to have a 5 min on 3 min off cycle all the time, or at least fairly consistently. I left the a/c on last night and by 6am the temp in the room was down to 74, so it will still cool, even with the 5 on 3 off cycle.

I suspect there is something wrong with the thermostat or temp sensor or something of that nature, but that is just a guess. We've had the unit since 2005. Thanks for any help you can give.

Please ask if there is any info I've neglected to give.

 

I took the front cover off to clean the evaporator with a small brush and noticed that when the compressor is on the evaporator coils at the bottom were cold and sweating (one was a little frosted), and the ones in the middle and top were cool but not cold. Since the outside temps have been hotter (upper 90 to low 100s) the compressor cycles have increased to anywhere between 7 and 9 minutes (usually). That's the only new info I have.