Microwave Fan Runs at High When in Use

[Jessd]

When my Maytag Over-The-Range Microwave Oven Model MMV1153BAS is
turned ON to heat, the cooling fan, which I believe is also the Vent Fan, runs
at HIGH. The manual states that this fan should run at LOW and only switch to HIGH when the temperature around the magnetron rises to a certain level.
Operated manually with the button on the touchpad, the Vent Fan runs normally at both LOW and HIGH. Anyone has a clue as to where the problem is? What component should I change?

[RegUS_PatOff]

MMV1153BAS Tech Sheet (http://www.servicematters.com/maytag_library/docs/16027123.pdf)

MMV1153BAS Service Manual (http://www.servicematters.com/maytag_library/docs/16027303.pdf)

The Wiring Diagram is confusing, and I may be wrong, but it doesn't seem possible if the HI & LO work OK fron the Touchpad...

[Dan O.]

[QUOTE=Jessd]

The manual states that this fan should run at LOW and only switch to HIGH when the temperature around the magnetron rises to a certain level.[/quote]Around the magnetron tube? Not the oven cavity or vent area?

In any case there must be a thermostat that is suppose to be detecting the temperature. If the fan is running at high all the time, maybe that thermostat has failed and giving inaccurate information to the control resulting in the increased fan speed?

There look to be at least 4 thermostats (see the following link) in various places on the unit. I don't know which one would specifically be for such a function on your model, sorry.

LINK > Maytag MMV1153BAS Thermostats (http://www.repairclinic.com/?searchtext=MMV1153BAS+Thermostat)


What component should I change?That will depend on which one is found to be defective.

If it is the temperature around the magnetron tube which actuates the high fan speed, one of the first that could be suspect and need testing might be the Magnetron Thermal Cut-Out (see the following link). It should read open (infinite resistance) only when overheated and closed (zero resistance) when at room temperature.

LINK > Maytag MMV1153BAS Magnetron Thermal Cut-Out (http://www.repairclinic.com/?searchtext=1145482)

LINK > How do I test for continuity? (http://acmehowto.com/howto/homemaintenance/electrical/continuitytest.php)

JMO

Dan O.
www.Appliance411.com
The Appliance Information Site (http://www.repairclinic.com/?searchtext=Maytag+Microwave)
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[Jessd]

Thank you Dan O for your reply.

I agree that the problem could be in one of the thermostats, possibly stuck at a position that switched the fan to High. Am I right in assuming that in this model, the cooling fan is also the vent blower? As to the magnetron thermal cutout, if it is open, then the microwave should not function. In the case of my microwave oven, everything else works normally. It is merely annoying (because of the noise) that the fan runs at High when it should be at Low.

To RegUS Patoff, thank you, too for the links to view the wiring diagram.

[Dan O.]

Your suspicion that a Thermal Cutout that opened, could be the problem makes sense. Could this be simply stuck in the open position?That would be how one would fail although if the fan speed change occurred regularly (ie. by design), I wouldn't expect a thermal cutout to be responsible. It sounds more like the operation of a thermostat. A thermostat could be stuck open or closed depending on how the particular one was designed to act to achieve the desired effect.

The only reason I suggested the magnetron cutout is because you said fan operation changed depending on the temperature around the magnetron tube and that's the only thermal component I see in that immediate area.

How can I get hold of a schematic/wiring diagram for this model?Besides the link RegUS_PatOff supplied previously to the 'tech sheet' (I guess you didn't check it out?), there should be one in the microwave... somewhere. On some OTR models it is often located in the vent area. I do not know on your specific model.

JMO

Dan O.
www.Appliance411.com
The Appliance Information Site (http://www.appliance411.com/parts/?ref411=Maytag+Microwave)
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