Defrost Control

Cathy for Model Number tbx18sa

Answer Cathy, This issue would most likely be caused by a bad defrost heater or the timer. You can check to see if the heater is good by turning the defrost timer until it clicks an then check to see if the heater is coming on. If the heater does not come on then the heater is most likely the cause and if heater does come on then the defrost timer would be the cause. 

Frank V. for Model Number tbx18jibqrbb

Answer Hello Frank, You need to begin the troubleshooting process with the unit frosted or at least after you let it run 24 hours. This is because the defrost thermostat can only be tested when it is below 20°F. Open the fresh food door and look at the control enclosure for a hole about 1/2 inch in diameter, (usually straight up). There will be a plastic "knob" inside the opening that can be turned with a small screwdriver. This is how the unit is advanced into the defrost cycle. As you turn it, you will hear it clicking. When it gets to the defrost cycle, it will click louder. Stop at this point. This is the beginning of the defrost cycle. Close the door and wait about two minutes. Now open the freezer compartment and look for an orange glow from the bottom "air grill" in the back wall of the freezer. If you see the glow, the defrost heater is energized and the issue is the defrost timer. The heater and defrost thermostat is verified good if the glow appears. If you don't see the orange glow, you need to remove the rear wall of the freezer compartment and test each side of the defrost thermostat for the 120Vac. If the voltage is on both sides of the defrost thermostat, it is good and you will need to use a resistance meter with power off to the unit to test through the defrost heater. Once you have located the bad part, you should allow the unit to sit in defrost with the unit plugged in for at least 45 minutes to make sure the timer cycles back out of defrost. This makes sure the defrost timer motor is good and advancing the timer properly. 

Steve for Model Number WR09x0520

Answer Steve, Based on the information. If you have the unit in a forced defrost and after 45 minutes the unit has not come out of the defrost, then the defrost control is bad. To replace the defrost control you would unplug the power and remove the cover where you turned the defrost control and take out 2 screws that hold the timer in place. Once removed you will disconnect the wires and install a new timer. If when you put the unit into defrost and if the ice on the coils did not melt then you would need to check the defrost heater and thermostat for continuity and if no continuity then replace the part. 

Frank V for Model Number tbx18jibqrbb

Answer Frank, You will want to first check to make sure that the fan in the freezer is operational. If not then check to make sure that it is getting 120 vac. If it is then replace the fan. If the fan is working then check to make sure that the evaporator coils are not impacted with ice. If it is then it sounds like you may have a defrost problem with the unit. Check and see if there is any frost build up on the back wall of the freezer. If so, you will need to test the defrost heater and the defrost thermostat. They should read closed for continuity when cold. You can test this with a multi-meter TJMA-DMT3. I will include a link at the end to assist you how to use the multi-meter if needed. If both parts are good, you will need to replace the defrost timer. Once the problem is repaired, you will need to thaw out the ice on the coils before the unit will operate properly. http://forum.appliancepartspros.com/oven-repair-including-ranges-cooktops/4810-how-check-continuity-ohmmeter.html 

Policka for Model Number TBX22PIYMRWW

Answer Hello policka. The thermostat is located on the top of the evaporator coils and the timer is located in the control panel section of the unit. 

Preston W. for Model Number TBX22PCSERWW

Answer Hi Preston. Look at the back wall of the freezer. If you see it has frost all on the front of it then you have a defrost issue. If the freezer fan (evaporator fan) is running then it is ok. Look at the controls housing. Find a hole the size of a nickel. Inside you see a slot where you can advance the defrost timer part # WR9X520 to the first heavy detent (click). This will stop the compressor run time for approx. 25 minutes and send the 120vac to the defrost thermostat part # WR50X10010. It is normally closed under the freezer temperatures. It sends voltage to the heater. Then the timer allows normal defrost of the evaporator coils. If the timer is difficult to turn, then replace it. The 2-wires from the defrost thermostat should read closed (0-ohms) on the volt meter part # TJMA-DM1,under frozen freezer temperatures. If it reads open-(Infinity) then you need to replace it. The heater part # WR51X465 needs to ohm out from 8-18 ohms, not open as well. If so replace it. It is a normal failure for a failure of this sorts on a aged unit. Usually the thermostat and the timer are the common failures. Use towels on the top shelf to catch the water as it defrost while working on the unit. Thank You