Freezer works, but bottom part does not get cold. Realized that the evaporator coil fan (?) was broken, so I replaced it in the top of the freezer. That did not fix the bottom part, it still fails to get below 75 degrees after having been on for 5 hours. Any suggestions?

Fan in freezer working? Any frost build up on inside back freezer wall?

Modern consumer refrigerators only have coils in the freezer. In the lower back of the freezer there is a small fan and possible a damper (flap that opens/closes) to push cold air from the freezer to the refrigerator. Given that the freezer is 18 deg, it's probably cold enough to keep the fridge area at typically 34 deg.
So the cooling system (compressor, coils, thermostat) are not working properly to keep the freezer at, typically 0 deg. Possible causes: partial loss of refrigerant gas, icing around evaporator coils (in freezer), compressor failing, dust clogging condenser coils (under fridge), condenser fan clogged or broken (under fridge), thermostat failure.
I'd start with condenser. Remove the slotted trim at the bottom front and look in with a flashlight. Are the coils clean? Pull out the fridge and remove the lower back cover (usually cardboard). You can now see the coils and fan. Clean and blow them out.
If it's icing, it probably means freezer door not closing tight. If auto-defrost not working properly it would probably get worse over the period of a few days so not likely.

Remember that most all refrigerators only have cooling to the freezer... the refrigerator depends on stealing some of that cold to be cool, so here's my top 3 guesses...
Cause 1 The defrost heater is defective, so frost accumulates on the evaporator coils, and the coils will become plugged with frost causing the airflow through the coils to be restricted, and the refrigerator not to cool. Check the evaporator coils to determine if they are frosted over. If the evaporator coils are frosted over, test each component of the defrost system after clearing any restrictions to the cooling fan and defrosting with a hair dryer.
Cause 2
The evaporator fan motor draws cold air over the evaporator coils and circulates it throughout the freezer. If the evaporator fan is not working, the freezer or refrigerator will not cool adequately. To determine if the evaporator fan motor is defective, try turning the fan blade by hand. If the fan blade does not turn freely, bench test it for function and use a multimeter to test the motor windings for continuity. If the windings do not have continuity, (very odd) replace the evaporator fan motor.
Cause 3
Damper Control Assembly The air damper control opens and closes to let the proper amount of cold air into the refrigerator compartment. If the damper does not open properly, it won't let enough cold air into the refrigerator. Check the damper control to determine if it is broken or stuck closed or that an inadvertent bump has shut it off to the refrigerator compartment

Remember that most all refrigerators only have cooling to the freezer... the refrigerator depends on stealing some of that cold to be cool, so here's my top 3 guesses...
Cause 1 The defrost heater is defective, so frost accumulates on the evaporator coils, and the coils will become plugged with frost causing the airflow through the coils to be restricted, and the refrigerator not to cool. Check the evaporator coils to determine if they are frosted over. If the evaporator coils are frosted over, test each component of the defrost system after clearing any restrictions to the cooling fan and defrosting with a hair dryer.
Cause 2
The evaporator fan motor draws cold air over the evaporator coils and circulates it throughout the freezer. If the evaporator fan is not working, the freezer or refrigerator will not cool adequately. To determine if the evaporator fan motor is defective, try turning the fan blade by hand. If the fan blade does not turn freely, bench test it for function and use a multimeter to test the motor windings for continuity. If the windings do not have continuity, (very odd) replace the evaporator fan motor. Cause 3
Damper Control Assembly The air damper control opens and closes to let the proper amount of cold air into the refrigerator compartment. If the damper does not open properly, it won't let enough cold air into the refrigerator. Check the damper control to determine if it is broken or stuck closed or that an inadvertent bump has shut it off to the refrigerator compartment

There are three reasons for your fridge problem. 1. Malfunction of defrosting. 2.Gas chocked.3.Thermostat setting.
1. The freezer can be set to atemperature between.
Thanks, helpful?
-14°F and 8°F.

Sounds like your evaporator fan is not doing its job. The purpose of this fan is to move cold air from the evaporator coil (behind the lining of the unit) to the rest of the freezer and to the refrigerator.

The fan should be behind an access plate at the top of the freezer compartment. If it is running, you should be able to hear it. If you don't hear it, open the access plate and look at it. If the fan is not turning, you will need to replace the fan motor.

Okay,
Defective compressor, refrigerant low from a leak in the system, dirty condenser coils, condenser fan not working, bad compressor relay or capacitor, main thermostat control not working, thermostat needs to be set at proper setting, frozen evaporator coils do to faulty defrost timer, defrost heater coil broken, or the defrost determination thermostat has stayed in the open position, which would result in no defrost and the ice blockage would stop air the circulation, defective evaporator fan, defective door switch which controls the evaporator fan when one opens and closes the freezer door. Freezer drain clogged which would possibly cause the fan to be stuck because of ice built up around it.

You are not moving air between the freezer and refrigerator sections. This may be due to a defective fan motor or a frozen evaporator coil.

PLEASE DISREGUARD GUEST FIXYA SOLUTION,FREEZER PROBLEM PROCEDURE IF NOT DEGITAL,FIRST CHECK IF ICE ON BACK FREEZER WALL. STEPS-FIND DEFROST TIMER,BOTTOM FRONT ,BOTTOM BACK, INSIDE FRIG.ON CONSOLE,LISTEN TO SEE IF FAN IS RUNNING IF SO TURN THE DEFROST TIMER CLOCKWISE TILL YOU HEAR A CLICK SEE IF FAN TURNED OFF IF SO YOUR FREEZER IS IN DEFROST,FREEZER WILL COME OUT OF DEFROST IN 20-30 MINUTES IF IT DOES AND THE FAN COMES ON YOU HAVE ELIMINATED DEFROST TIMER&FAN,NEXT REMOVE BACK PANEL TO FREEZER IF THERE IS ICE FORMING REMOVE BOTH LEADS TO HEAT AND CHECK WITH VOLT METER ON OMES,IF YOU GET ANY READING THE HEATER IS GOOD,IF NO READING REPLACE HEATER AND CLIPON TEMINATOR,IF HEATER IS GOOD DEFROST COILS WITH HAIR DRYER TOP TO BOTTOM AND THIS WILL ALSO CLEAR THE DRAIN,IF EVERYTHING CHECK OUT GOOD DEFROST TIMER ,FAN ,HEATER, DRAIN, YOU NEED ONLY TO REPLACE THE LITTLE ROUND CLIP ON TERMANATOR,LET ME KNOW-MIKE

It sounds like cold air from the freezer isn't making it to the fridge compartment. This can be cause by a several things. The damper that lets air into the fresh food side is stuck in "closed" position, the temp sensor (t-stat) isn't working properly, the evaporator fan (in the freezer comp above the coils) isn't working to blow air up to the fresh food section. In some situations, the defrost cycle for the freezer section isn't working and the coils have frozen into a block of ice and air can't flow over them properly so you get not cold air to the fresh food section but the freezer still stays cold due to the block of ice.