When should which fans run?

The only fan that runs while using Microwave (only) mode is the electronics compartment cooling fan. I'm pretty sure that when new (unit ~ 2 yrs. old), the convection fan motor also ran, circulating air within the cooking chamber even during microwaving (only) use. The convection oven fan runs when in Convection (only) mode. The oven (chamber) light operates normally, the unit heats well in Microwave (only) mode, but when new a fan ran, quite audibly (which fan? No idea! However, NOT the cook top over-temp fan, which I believe is also the Vent fan.) that is not now running, or else the electronics cooling fan got unusually quiet for no reason. The cook top Vent fan seems to run normally, switch controllable.

Stirrer motor/ turntable motor/ damper motor all seem to operate normally.

The troubleshooting guide that's part of the wiring diagram (P.N. 3840W1T150E) included with the machine is insufficient for the purpose of determining the sequence of events for the various operating modes. (The wiring diagram itself is wrong also, but that's another question...)

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Hi,

Hopefully I've got the right model number for your oven. I went by the information that I got when I clicked on the link to the right of your question. It says GE Profile microwave-convection-over the stove top oven. PN PVM9179DF1WW Repair

From what I can ascertain from the spare parts list for that oven is that there are 3 fans.

(see link http://www.searspartsdirect.com/model-nu... )

1. A ventilation motor (Part #: WB26X10100 Substitution: WB26X10269) seen in this link No. 1258 on drawing

http://www.searspartsdirect.com/model-pa...

2. A circulating motor (Part #: WB26X10185) seen in this link No.1417 on drawing http://www.searspartsdirect.com/model-pa...

with a Fan (Part #: WB38X10099) seen in this link No.80 on drawing

http://www.searspartsdirect.com/model-pa...

3. A Microwave cooling fan blade (Part #: WB38X10005) seen in this link No.417 on drawing and Motor AC Fan (Part #: WB26X10247) also seen in this link No.518 on drawing

http://www.searspartsdirect.com/model-pa...

According to the user guide, the vent fan automatically turns on to protect the microwave if it senses too much heat rising from the cooktop below. Maybe this is what you heard before.

There is also this statement from the user guide under "things that are normal with your microwave oven"

The vent fan operating while the microwave is operating, The vent fan will not go off nor can it be turned off until the microwave is off.

You said that the microwave fan has gone very quiet. Are you certain that it is working? Can you get to prove that it is. This link may help.

https://www.youtube.com/watch?v=t1tdj3On...

Perhaps this information in conjunction with the information that you have, will enable you to resolve your problem.

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Hi, J;

I can't figure out how to respond directly to you; hope this works O.K.!

The (1.) item mentioned above is the over-the-stove vent fan. It's a 300 CFM squirrel cage, so it's pretty easy to identify from the noise. Yes, it comes on automatically when the cook top gets too hot.

Item (2.) above is the "stirrer" motor, which is a synchronous, slow moving motor meant to distribute the microwaves. Pretty silent.

Item (3.) is the actual electronics compartment cooling fan, and it is indeed working, seems to be about the correct speed, but I don't know that for sure.

The item I suspect is link # 519 (PN WB26X10256), used as the convection oven circulating fan. What I don't know is whether this fan is also used during the microwave (only) mode. When new, a paper towel placed over the heating vessel rippled energetically; now it doesn't. Unfortunately, I never knew which fan was responsible for that agitation to begin with, and I'm having a difficult time finding out the answer now!

Thanks for your help!

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Hi Doug,

Why do you think that the fan you mention #519 (sorry I missed that, past my bedtime I think)should also be working with the microwave? From what you are saying, that would possibly mean that there could be 3 fans on during microwave operation - electronic cooler (on in most microwaves), stirrer fan and convection fan. Makes it seem like it is a "fan forced" microwave oven as well as a "fan forced convection oven. I didn't think that micowaves cooked that way. I always thought that they cooked from the "inside" of the food by agitating the atoms thus generating heat. Learn something new all the time, I mean if it is a extra way of distributing the radiating heat from the food to aid cooking.

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Hi, J;

Thanks!! You're right, I _do_ believe the convection fan, the electronic cooling fan and the stirrer _should_ be on during microwave operation. The reason I think that is because - assuming I'm not losing my mind - when new, a paper towel placed over say, a cup of coffee, was agitated quite a bit during microwaving, and the sound indicated a fan of some kind was running. That no longer happens, either agitation or noise, although I can _see_ the electronic cooling fan running. Inspection of the whole works makes me believe the only fan that has access to the inside of the cooking cavity is the "convection" fan, which would mean the "convection" fan does double duty. IF that's the case - which is what I can't seem to ascertain - then the control board has to be faulty, since the fan works just fine in "convection" mode. Unfortunately, I can't locate any friends with a similar unit for observational purposes, GE "customer no-service" won't tell me, and I can't find a control board schematic.

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Hi Doug,

Maybe you could contact an other "authorized"service centre - not GE - and ask them to confirm your suspicions.

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Thanks, J, that's a good idea. Now I just have to _find_ one willing to talk to me! If I can just keep my wife from killing me for another few days... Any ideas where to look?

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Doug will be eternally grateful.
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