I cannot find my defrost timer on my GE modelsPDS22SFSBLSS

SOURCE: Frozen Freezer Coils

all of the above the heater is on the coil you will seethe wires the therm. is on the top of coils timer could be at lower back of refrig.

SOURCE: not defrosting

first thing is to check the defrost heater if it looks black it is bad the part number for the heater is wr51x10053
i have replaced a ton of these

SOURCE: GE GSL22JFPH BS refrigerator, coils icing up

I'm in the process of fixing the same problem on a GSS22JEPDWW right now. There are several parts in the defrost circuit that I can tell:
1) Defrost Heater
2) DefrostThermostat
3) Temp Sensor (Thermistor)
4) Main Control Board
I've replaced the Defrost Heater (remove back panel of freezer section - it's a stainless steel bracket that has a glass bulb in it) and it still doesn't work. The main control card provides power to the heater 4 times every 24 hrs for 25 minutes or so to defrost the evaporator coils. If all items are working, you'll see water in the drip catch at the bottom inside of the freezer compartment. Better yet, pull the refer away from the wall for 24 hrs and check if water is gathering below the plastic drain on the right rear of the refer in the pan. The water drips into a pan and the fan for the condensor coil evaporates it. Go to the www.ge.com website and look in the service section to find the parts diagram for your refer. You can then get a part number to buy the parts you need from a local parts store or the Internet.
I just bought the thermostat a few minutes ago and will try that next. Heater was $37, thermostat was $15. Sensor is about $20 and the control card is $140 (you can find on line for $95). I'm going down that path. If none of this works, it'll be in the dump in a week.
I've learned on-line GE refers are bad news. The control cards can fail repeartedly, althoough mine has worked for over 4 years. But, I won't ever buy another one since refers should last at least 15 years in my book. After $200, it doesn't pay to throw more good money after bad. I'll keep you posted on my results.
TM

SOURCE: GE refrigerator TBX25zpk coils Freezing

It's almost always the defrost heater. If you have volts to the defrost thermostat the defrost control is working. Set your meter to check ohms and remove the wiring from the heater. If anything changes when you touch the meter leads to the heater terminals then the heater is probably good, but my guess is nothing will change, which means you've got a bad heater.

SOURCE: freezer freeze up

Your model TFX20JRBKWWW uses a defrost timer part number WR9X489 located behind the light shield in the fresh foods compartment. (top back area). Just in case you need to know, the defrost heater is a part number WR51X10101 located behind the back wall of the freezer.