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Parts for Maytag MZD2766GEW Refrigerator - AppliancePartsPros.com
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Here is the operators manual.
http://www.maytag.com/digitalas...Guide%20-%2061005298.pdf

Your repairman is sort of correct.
If you look at the damper (Housing Assy) (item 8 in section 02) you will see that it includes a thermostat that open and closes the louver which regulates the amount of cold air entering the fresh food section.
But item 4 does give you some control over this.

Check you freezer temperature. it should be between 0 and 5 degrees F.
It does have an effect on the fresh food section.

I do not know who SandraK is but you could reply on her post and then with luck she will get back to you.

Note that it will take quite a while for you to see temperature changes when you change a setting.
Especially if there is a lot of food in a compartment as everything in the compartment must come to the new set point temperature before a thermometer will register the final temperature setting.

I cannot say if changing the damper will solve the problem.
That it is regulating the temperature at 40 does seem to indicate that it is working.

Also is the compressor cycling as it normally does?
Or is it on all the time which would indicate a different problem?