Question about Whirlpool MH1150XMQ Microwave Oven

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Starting Capacitor I was told to replace the starting capacitor on my Frigidaire Microwave in order to get the exaust hood fan to work again. (it now just hums) Do you know if this is a dangerous part to be coming in contact with.-I have read all sorts of precautions. What would you do? Thanks-Bob Mc

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Found this Frigidaire question posted under Whirlpool but I'll be happy to answer just the same.

The starting capacitor is connected to the line level voltage, as opposed to the high-voltage capacitor evryone warns about.

The starting cap doesn't store enough of a charge to worry about.

The main thing is to be sure the oven is disconnected from the power line. I prefer unplugging it, but some installations make that hard, so you need to turn off the breaker.

Hood fan failure can happen due to many causes:

If a cooktop light bulb blows or is removed or installed while the oven is still connected to the power line, that can damage the circuit board in the area.

The hood fan motor wiring can short.

The starting capacitor can be bad.

There may be dust, hair, debris, etc. in the bearings of the hood fan motor jamming it. The filters are supposed ot help prevent this, but things happen.

Behind the control panel on Whirlpools is a very helpful mini-manual that can help you check and diagnose quite a few problems with these.

On some brands it's located on the control circuit board, in others it's mounted on or in the hood fan assembly.

If you post your brand and model we can probably steere you better on a mini-manual and the capacitor.
Starting Capacitor - dfbb857.jpg

Posted on Dec 04, 2007

  • William Miller
    William Miller Dec 04, 2007


    To clarify, I was referring again to the capacitor when I said this:

    "On some brands it's located on the control circuit board, in others it's mounted on or in the hood fan assembly."

    My transition was a bit rough, I may have had you thinking I was talking about where the mini-manual might be located.



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Sanyo EM-SL40S microwave everything seems to be working fine but food doesn't get hot?

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A diode is an electronic component that readily passes current in one direction only and blocks the flow of current in the opposing direction. If your microwave's diode has become defective, your microwave will not heat and you will hear a buzzing noise. Test the diode to determine if this is the cause of your problem. Replace it if it is defective.

High Voltage Capacitor

A capacitor is an electrical device which stores electricity. A defective capacitor may be why your microwave is not heating but you are hearing a buzzing or humming noise. The capacitor will have to be tested to determine if this is the cause of your problem. A defective capacitor will have to be replaced before your microwave will work again. Make sure you discharge the capacitor before you test it, though.


A defective magnetron is the third possible cause of why your microwave is not heating, but you can hear a buzzing noise. Test your microwave's magnetron. Replace it if it is defective.

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Needs new exhaust fan start capacitor

The motor run capacitor for this model (C100 on the power board) is a 7uF 230V type and the part number is RC-QZB014MRE0.

You can order parts from Encompass here or you can call them toll-free at 866-779-5835.

Or a local appliance parts store may have that one or one close enough to work, as long as it's rated at 230V or greater and about 7uF (microfarads).

It may not be a bad capacitor, it may just be a bad solder connection at the capacitor, or possibly at the relay that runs the hood fan (RY6) or the connector CN-A.

Lastly, the bearings in the motor may be dry or dusty.

I would check the connections on the control board first.

We have the service / repair manual for this model and have uploaded it to our site here for free download to help you.

It will give you safety info, step by step help in disassembly, and troubleshooting tips, but it does not show the capacitor part number.

Since this is made for Frigidaire/Electrolux by Sharp, I got it from another Sharp manual. This capacitor is used in several Sharp models.

We're happy to help you with free advice and we'd appreciate your thoughtful rating of our answer.

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Frigidaire Microwave plmv169dcd Start Capacitor

The starting capacitor is used to start the hood vent fan motor. It's also called the hood capacitor.

On page 8 of the document you refer to above, on figure O-1, you will find the hood capacitor. It is shown on the control unit (circuit board). I've attached a snapshot of that area below.

Its leads connect to terminals A1 and A3. The hood fan red wire goes to A1, and the yellow wire goes to A3.

That part is not shown in this document as a separate part, so you will have to get it generically from an appliance parts store or electronics supplier, but you will have to order it by value.

You need to look on it and it will say something similar to this:
"7 uF 230V". In this example, that would be a 7 microfarad, 230 volt capacitor.

It's okay to get a capacitor with a little higher voltage rating, but not lower.

The capacitor, if truly bad, may not look bad. It can be quick-checked with an ohmmeter to see if it will charge and discharge (the meter will first indicate low resistance then go high to infinity). This is not a full-blown test, but for this kind of capacitor it may be enough.

You should check the solder connections, also. It's a large part, and sometimes they don't get enough solder on them. The connection may be cracked and just need to be resoldered.

Since a new thread was started, it makes it harder to follow along the saga...

But this problem could be a bad (or jammed or obstructed) hood fan motor, a flaky relay on the control board, a bad cap, or bad wiring.

Microwave hood fan motor starting capacitors usually look something like this, and may be red, blue, green, orange, etc.


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"Starting Capacitor"

I just posted an exhaustive answer to this on another new thread you just started. This makes thread number five on this issue.


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Frigidaire PLMV169CD Micowave Hood Vent fan Hums but won't run

The starting capacitor will be on the circuit board. You need to remove the control panel to see it.

You can usually find helpful exploded view diagrams and order parts by entering your full model number here:

We have *critical* safety, disassembly, and troubleshooting info at our site, which is linked at our listing here on FixYa:

I am beginning to suspect that you have a failing relay on the control cirucit board. It may have arced and gotten carbon deposits on the contacts, reducing the conductivity. This means less current flow and reduced or non-existent fan action.

After you've checked all this, feel free to contact me about a possible repair. We could have you send us the control panel assembly and the new hood fan so we can analyze and repair it. The second link above takes you to our site.

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Frigidaire PLMV169CD Micowave Hood Vent fan Hums, but won't run

If you have an old analog multimeter, you can put it across the motor start capacitor and the needle should deflect to low ohms position then ramp up to the open or infinite ohms position. You can remove it and test it the same way. Also, doing this test should store a dc voltage on the leads which can then be read even with a digital multimeter. I have even used an audio output from a cheap amplifier to determine if audio is transmitted from one lead to another. The capacitor works by shifting the starting current by 90 degrees and the motor acts as you say it does if the cap is bad. Make sure you orient the cap properly with the positive and negative terminals in the proper holes

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Frigidaire PLMV169cd Microwave Exaust Fan Hums but wont run

Do you mean the hood vent fan? (That would be a large assembly a little smnaller than a loaf of bread, I guess)

If it's this one, I would suggest you check the big starting capacitor on the circuit board and the connections on that cap.

Or do you mean the cooling fan inside, which would be small enough to basically fit in your hand?

In either case, I would measure the line voltage to be sure it's in the 110-125VAC range.

If it's grossly outside this range, you may have a problem with other electronics or light bulbs bblowing or being dim or erratic.

One handy thing about Whirlpools is that behind the control panel they have a mini-manual which is very useful in troubleshooting.

It may be that you have some toruble on your control board, which we repair for customers nationwide.

Please write back with more details if you need further help.

We're happy to help and we appreciate your thoughtful rating of our answer.

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