After maintaining -30, the freezer was found at +30 and products were thawing/melting - Is the defrost timer bad? Or thermostat?

Is the compressor running? If not - the timer could be stuck in defrost mode. If it is ruinning, then the freezer coil should be cold. If it is choked with frost & ice - then the defrost heater isn't getting powered (bad timer or defrost terminator - or is getting powered but has burned out.

You should allow the ice and frost to melt completely before turning back on again. Typically ice and frost don't build up so bad in a few days time to cause the temperature rise you're describing If getting cold - the compressor and refrigerant is likely OK, if not the defrost circuit is suspect. If compressor running but not getting cold - a refrigerant leak / charge level may be causing the problem.

The problem is with the "thermostat" right next to the defrost timer. When you tap on the control, you are actually tweaking the thermostat and not the defrost timer. Here is the thermostat to order.
Here is a diagram of the control box. The thermostat is number 13 and the defrost time is number 4.

Sounds like your defrost thermostat is not working.

The evaporator coil behind the cover on the back wall inside the freezer will ice up under normal conditions. Every 8 to 10 hours for around 20 minutes the defrost timer (or in most newer models the electronic adaptive defrost control) will turn the defrost heater on to melt the built up ice. There is a defrost thermostat which prevents the heater from overheating the freezer by breaking the heater circuit when the temp reaches close to 32 degrees F. The entire cooling system shuts off during the defrost cycle and starts back when the timer advances through the cycle.

If this ice is not melted it will continue to build up until the air can't flow over the coil to circulate the cold air through the freezer and into the fridge. The temperature change in the fridge is usually noticed first followed by the freezer.

If the defrost thermostat is bad, it can prevent the heater from coming on OR it won't turn the heater off when it gets too warm. It is clamped to the evaporator coil at the top to sense the temp. If it appears to be misshapen it is bad.
With an ohm meter it should show continuity when cold and none when warm.

With the defrost timer being replaced already it sounds as if the repairman is not looking at the real problem. Unit works for 2 days then things start thawing. Hint Hint... it is not defrosting. There is a heating element inside the freezer section attached underneath the internal tubing that melts the ice every 6 to 8 hours via the defrost timer depending on the defrost timer installed. To prove that it is not defrosting..... just unplug the unit and place a stand fan blowing into the freezer for about 90 minutes. I would bet that once you plug it back in it wil work for 2 days and the problem once again repeats. With 2 calls on the same unit and you still have the same problem I would be calling the service people back and demand they fully troubleshoot the defrosting element and thermostat. Personally this is an unstatisfactory performance of an in home service by a repairman. With the exception of a new part if required, they should wave any labor and service call fees.

Normal 0 MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman";} The evaporator coil behind the cover on the back wall inside the freezer will ice up under normal conditions. Every 8 to 10 hours for around 20 minutes the defrost timer (or in most newer models the electronic adaptive defrost control) will turn the defrost heater on to melt the built up ice. There is a defrost thermostat which prevents the heater from overheating the freezer by breaking the heater circuit when the temp reaches close to 32 degrees F. The entire cooling system shuts off during the defrost cycle and starts back when the timer advances through the cycle.

If this ice is not melted it will continue to build up until the air can’t flow over the coil to circulate the cold air through the freezer and into the fridge. The temperature change in the fridge is usually noticed first followed by the freezer.

If the defrost thermostat is bad it can prevent the heater from coming on OR it won’t turn the heater off when it gets too warm. It is clamped to the evaporator coil at the top to sense the temp. If it appears to be misshapen it is bad.
With an ohm meter it should show continuity when cold and none when warm.
You can also bypass the thermostat to see if the heater comes on then. If it does then you know the thermostat is bad and needs replaced.

The defrost heater is located on the evaporator. It is in a tube which is at the bottom and can also go up the sides of the evaporator. On some types you can see a burnt spot if it’s bad. With an ohm meter it should show continuity from end to end when disconnected from the wiring in the freezer. You can also test the wiring for voltage when it’s in the defrost mode.

If you have a defrost timer you can test it. It can be located under the fridge behind the kick panel on the front. Some are in the fridge with the controls at the top. You can turn the defrost timer till it clicks and everything shuts down. The heater should now come on. If it does, replace the timer because that means the timer is not running. If it doesn't, check the heater and defrost thermostat. Turn the timer again till everything starts back up to end the defrost cycle.

If you have an adaptive defrost control instead of a timer, replace it if the heater and thermostat test good. It is located in the fridge with the controls in some models and on the back in others.

The evaporator coil behind the cover on the back wall inside the freezer will ice up under normal conditions. Every 8 to 10 hours for around 20 minutes the defrost timer (or in most newer models the electronic adaptive defrost control) will turn the defrost heater on to melt the built up ice. There is a defrost thermostat which prevents the heater from overheating the freezer by breaking the heater circuit when the temp reaches close to 32 degrees F. The entire cooling system shuts off during the defrost cycle and starts back when the timer advances through the cycle.

If this ice is not melted it will continue to build up until the air can’t flow over the coil to circulate the cold air through the freezer and into the fridge. The temperature change in the fridge is usually noticed first followed by the freezer.

If the defrost thermostat is bad it can prevent the heater from coming on OR it won’t turn the heater off when it gets too warm. It is clamped to the evaporator coil at the top to sense the temp. If it appears to be misshapen it is bad.
With an ohm meter it should show continuity when cold and none when warm.
You can also bypass the thermostat to see if the heater comes on then. If it does then you know the thermostat is bad and needs replaced.

The defrost heater is located on the evaporator. It is in a tube which is at the bottom and can also go up the sides of the evaporator. On some types you can see a burnt spot if it’s bad. With an ohm meter it should show continuity from end to end when disconnected from the wiring in the freezer. You can also test the wiring for voltage when it’s in the defrost mode.

If you have a defrost timer you can test it. It can be located under the fridge behind the kick panel on the front. Some are in the fridge with the controls at the top. You can turn the defrost timer till it clicks and everything shuts down. The heater should now come on. If it does, replace the timer because that means the timer is not running. If it doesn't, check the heater and defrost thermostat. Turn the timer again till everything starts back up to end the defrost cycle.

If you have an adaptive defrost control instead of a timer, replace it if the heater and thermostat test good. It is located in the fridge with the controls in some models and on the back in others.

The defrost cycle is not working properly, there are three things involved in system. #1 Defrost timer in refrigerator #2 Thermostat on coils to tell if unit is frozen #3 heater element located under coils thaws coils when frozen. the defrost timer if it is manual < located at the front of light assembly panel in top of refrigerator there will be a hole with a plastic piece that resembles a screw strait screw head> it turns and every 8hrs aprox. it stops operations and starts defrost cycle by allowing voltage to the thermostat and if thermostat is frozen it allows power to element for thawing coils. If defrost timer is manual look for direction it is facing and mark edge to see if timer is turning< very slow turning and is easiest way> if you can get an ohm meter ohm the element on high setting< if it has continuity element is operable> check wiring just to be sure not problem. If you find the timer does turn and doesn't stay in one position over 40 minutes then the thermostat is bad.If element fails tesing then the element is bad and if timer stays in one position then it is bad. If unit is equiped with electronic defrost timer and element is good in would replace timer and thermostat to guaranty that resolved problem

there is an issue with your defrost. either your bi-metal thermostat, your defrost heater or your defrost timer/control are bad. you can check the thermostat and the defrost heater with an ohm meter on tone. they are both located behind the back panel in the freezer. ( Note: do not thaw freezer until thermostat has been checked, otherwise it will test bad due to warm temp ). if both thermostat and heater have tone, then the defrost timer/control is bad. Joe

• yes, refrigerators have heaters in them to defrost the buildup of frost around the coils
• they defrost approx. every 12-16 hours
• if the defrost cycle gets stuck then it will continue to heat
• i have seen it melt the plastic inside the refrigerator
• 
  
• possible causes:

1. bad defrost timer
2. bad thermo switch in freezer

• i would replace both as they are not expensive

EITHER replace or re adjust the THERMOSTAT TIMER MODULE , HOPE IT HELPS AJ