Hi,

My refrigerator freezes up every 5,6 days.

I have changed control assy temp but it did not help.

Is it possible the Heater & Therm problem?

I opened it, it looked normal. In the past it burned out once few years ago (it turned out my Frig was recalled due to overheat of an electric component. Maytag already changed the incriminating component).

What would you suggest to resolve this problem?

Thank you

check your thermal cut out, small round disk looking thing attached somewhere near the heater. if the center looks pushed out that could be the problem (it is a silver disk with a rubbery looking top...usually red black or blue) or your heater could be bad or the defrost timer.

[COLOR="Blue"]The evaprator freezes up so the fan could not move the air to the refrigerator compartment.
I think the defrost is not working but not sure.[/COLOR]
Yes, it does sound like a defrost problem

[COLOR="Blue"]The part I changed is Control assy., temp.
Part Number: AP4070269 made by WHIRLPOOL[/COLOR]
This part will not repair a defrost problem, it controls the units temperature.

[COLOR="Blue"]Do I have to change the heaterHeater & therm. assy
Part Number: AP4069923 ?[/COLOR]
This may fix the problem but I would do some troubleshooting first.
There is a 99.999% chance that either the heater & therm assembly OR the adaptive defrost board (Item 13 in Section 2) is the culprit.

First remove the evaporator cover in the freezer so you can see the coils.
Do not let them de-ice.
If they are heavily iced/frosted over you have a defrost problem.

If yes.
Manually force a defrost cycle.
Here is a link to forcing a defrost the first and last paragraphs on the page are for Maytags.
http://www.applianceaid.com/adaptive_defrost.html
With this unit I think to force a defrost, with the unit on and the compressor running turn the temperature control on/off 3 times in 6 seconds. The compressor and fans should then turn off with the temperature control in the on position, you are now in a defrost cycle.
Now check the defrost heater to see if it is on.
Be careful you do not want to burn your fingers.
If the heater is on then the board needs replacing.

If not on.
Unplug the unit.
Disconnect the heater & therm and measure across the heater for continuity, usually around 20 ohms or so.

If the heater is OK
Measure across the defrost thermostat (Item in Section ) and measure it, should be 240,000 ohms when frozen. Note that it opens just above freezing so must be frozen to check it. Also inspect it, if it is bulged at all replace it even if it measures OK.

If both the above are OK then odds are the board is toast.
Best way to test this is a live test to see if you have 120 volts across the heater/defrost thermostat combo.

If you do not own a meter, I would suggest you purchase a one. You can get a decent digital multimeter for under $20.00. You do not need fancy though it is nice if the leads are a couple feet long.
If it saves ordering one unnecessary part it has paid for itself and you end up owning a useful tool.
Most places will not let you return electrical parts so if you order it, you own it.
A couple things to watch when measuring ohms and continuity
1. Always remove power from the machine otherwise you could blow your meter.
2. Always disconnect at least one side of any device you are checking. This eliminates the possibility of measuring an alternate/parallel circuit path.
3. When checking for closed contacts and continuity use the lowest scale (Usually 200 ohms). Then try higher scales. This scale is 0 to 200 ohms so if the device you are measuring is 300 ohms this scale would show an open circuit which it is not, you are just measuring outside the scale's dynamic range.

There is a good STICKY at the start of this forum about it's use.