Fridge side won't regulate temp. however the freezer will freeze to -9 and stay right there! How do you test the thermostat? or is this a common problem. The fridge was built in 01' and nothing has been repaired in the past.

first run the diagnostics on the unit from the tech sheet inside the unit,then if thermistors are bad replace these there are 2 one on the left and one on the right wall in both fridge and freezer,if good per diagnostics then replace the electronic damper door located between the fridge and freezer compartments in the upper left hand corner of the fridge behind the plastic grille as these doors break and jamb open or shut and the temps can no longer be regulated during the diagnostics tests you can hear this door operate if its operating correctly,lastly,if these fail to solve your problem,replace the main control board in the back behind a panel

I would think first of the defrost termination thermostat malfunctioning.
This would vary the defrost time since it regulates the defrost time by temperature.
This is the most common failure in fridges next to start relays.
It is a two wire item in the freezer section which is clipped onto a tube. It senses
line temperature and turns off the defrost element when that temp is reached.
Should be located in the freezer section behind the back panel. Model and serial
number should be inside the refrigerator compartment, Part should be available
at an appliance parts store. Hope this helps.

The thermostat is likely failing intermittently, or the defrost timer could be failing.

Both parts can be tested (and should have been) by the repairman.

The defrost timer turns on and off to let the coils defrost - but if it stays off - can cause the rise in temperature. The thermostat, however, reports the temperature to the timer, so either (or both) could be to blame.

Have them tested.

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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(disconnect the two wires plugged into it and twist them together) 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.

HI!!

The little fan inside the freezer is the one in charge of blowing cold air into the fridge area, the freezer control (thermostat), regulates how cold it should get, and the Refrigerator control regulates how much of this cold air goes to the fridge compartment. It is important to keep the door gasket clean at all times in order to have a good thight seal.

Check:

1.- That the freezer and fridge controls are set correctly, acording to manufacturers specs. (a common problem arises when by accident, the temp. controls are moved out of preset adjusment.

2.- That the fan is working and sounds strong, (If you keep the freezer door open for a couple of minutes, you should hear and see the motor kiking in.)

3.- Find the vent(s) in the fridge compartment and feel if cold air is coming thru when fan is working. If fan is working and blows no air, Take the freezer's back panel off, (4 hexhead screws) just enough to see inside and check if the evaporator (radiator looking component) is covered with ice, blocking the flow of air towards the fridge compartment, if it is, your defrost thermostat and-or timer are defective.

Your temp control for the fridge when you first start it, should be a bit higher than the one for the freezer. (the freezer should be in the low-middle range.) This control is nothing but a actuator for a door that controls the flow of air from the freezer. The bigger the number, the wider the door opens, and the colder the fridge gets.

Once the system is stable, let's say the next day, you can re-adjust your controls, (don't expect an inmediate change right away, change one digit a the time and check again next day) If you set your fridge too high and the freezer too low, the freezer may loose coldness and the problem would invert.

Good Luck!!!

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 fridge gets its cold air from the freezer through a vent(damper) between the freezer and fridge.The fan in the freezer blows air through it. There is a flap you adjust with the fridge temp. control. Make sure it's opening and closing when you adjust the fridge temp ..
If the evaporator coils behind the back panel of the freezer are icing up because of auto defrost failure that will stop the circulation of cold air and eventually affect the freezer too.

check defrost timer, defrost heater, defrost thermostat. In most newer models the timer has been replaced by an electronic control board. If the heater and thermostat are ok it’ll be the control.

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. If it doesn't, check the heater and defrost thermostat. Turn the timer again till everything starts back up to end the defrost cycle.

How to check everything
http://www.acmehowto.com/howto/appliance/refrigerator/refrigerator.php

How to check everything
http://www.acmehowto.com/howto/appliance/refrigerator/refrigerator.php
The fridge gets its cold air from the freezer through a vent(damper) between the freezer and fridge.The fan in the freezer blows air through it. There is a flap you adjust with the fridge temp. control. Make sure it's opening and closing when you adjust the fridge temp .

OR.
If the evaporator coils behind the back panel of the freezer are icing up because of auto defrost failure that will stop the circulation of cold air and eventually affect the freezer too.

check defrost timer, defrost heater, defrost thermostat. In most newer models the timer has been replaced by an electronic control board. If the heater and thermostat are ok it’ll be the control.

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. If it doesn't, check the heater and defrost thermostat. Turn the timer again till everything starts back up to end the defrost cycle.

the dampener door in the fresh food is more then likely broke . allowing air in to the fresh food.

Faulty air damper is the usual cause , or possible sensor fault