Question about Whirlpool MH7140XF Microwave Oven

1 Answer

Whirlpool mh7140xfq I saw a posting you left for Ruby589 wanted to ask you about it. I also have this model microwave and suspected the diode. Please check my entire trouble posting or just see the latest trouble info below: Still not working even after replacing diode. Everything else checks out according to tech sheet from inside unit. Seems to be getting 120v to transformer primary, just no heat. By the way, I have never been able to get either diode (new or old) to show any continutiy in the forward direction. I have tried 3 different DMMs with same results. Could I have gotten a bad diode from the parts house or is this just a Fluke? (pun seriously intended). I feel that I am missing something basic. Help with how to check high voltage &/or magnetron side would be appreciated. I suspect that my capacitor is never seeing any charge. Thanks!

Posted by on

  • mspauld Oct 23, 2008

    Thanks so much! I've worked on and around various electrical/electronic systems for years but have never had much to do with microwave ovens. I'll probably take one more stab at troubleshooting b4 I just decide to replace the unit with a new oven. I see that my diode was probably good all along since it ain't shorted. Also I probably am not seeing anything to discharge at the capacitor due to the internal "bleeder" resistor. Again, nothing looks out of the ordinary inside and all resistive checks seem ok. I'll go back over them again tomorrow nite. Thanks so much for taking the time to respond to my trouble. You have been most helpful.



1 Answer

  • Level 3:

    An expert who has achieved level 3 by getting 1000 points


    An expert that got 20 achievements.


    An expert that got 10 achievements.


    An expert that got 5 achievements.

  • Whirlpool Master
  • 9,086 Answers

Here are some links you can use for test help, but read the safety warnings first: (if it is NOT shorted, it's probably fine) (if it is NOT shorted, it's probably fine)

The average DMM doesn't have a high enough voltage to bias a high voltage diode, which is several diodes is series.

If the diode was not shorted, it was probably okay. They almost always short when they go bad.

I don't advise people on measuring a microwave's high voltage. The voltages can be instantly lethal.

The tech sheet should show you how to measure the resistance of the windings of the high voltage transformer. You know you're getting 120V on the primary.

The capacitor is probably okay because they usually short when they fail, and that would blow the fuse when you hit Start.

Look for corrosion or signs of melting on the FA terminal of the magnetron (and on the other temrinal if someone reversed the wires). Look fro a loose connection at the magnetron.

If these connections are fine, then you probably have a bad magnetron.

Probably the best prices on Whirlpool parts can be had here.

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

Posted on Oct 23, 2008



1 Suggested Answer

  • 2 Answers

SOURCE: I have freestanding Series 8 dishwasher. Lately during the filling cycle water hammer is occurring. How can this be resolved

a 6ya Repairman can help you resolve that issue over the phone in a minute or two.
Best thing about this new service is that you are never placed on hold and get to talk to real repair professionals here in the US.
click here to Talk to a Repairman (only for users in the US for now) and get all the help you need.

Posted on Jan 02, 2017


Add Your Answer

Uploading: 0%


Complete. Click "Add" to insert your video. Add



Related Questions:

1 Answer

I am not sure which part I should be buying so that I can replace it in my microwave. The roof of the microwave has been perferated due to catching fire. It seems the microwave would still heat something,...

It sounds rather like you need a new internal casing. Given that the oven would need to be almost completely dismantled, the cost will likely approach that of a new oven. You might be able to make it an insurance claim.

If you try to fix it yourself, be aware that microwaves usually have a high voltage capacitor in the magnetron circuit, and you MUST make sure this is completely discharged before handling it anytime.

I don't want to post any more information on that here, just to say you would be best off getting a cost estimate from a competent service tech.

Sep 01, 2013 | Whirlpool Microwave Ovens

1 Answer

Whirlpool MH7140XFQ Fuse to Breaker Problem

There is absolutely no way to guess at the problem. You need to troubleshoot the circuitry with a meter to find the failing component

Oct 06, 2009 | Whirlpool MH7155XM Microwave Oven

1 Answer

MH7140XFQ Fuse Amp

you need to look at the ends on your fuse and this will tell you the amperage you need to get for your particular unit,get them from a hardware store

Sep 22, 2009 | Whirlpool MH7155XM Microwave Oven

1 Answer

I have a whirlpool model MH7140XFQ and we got a guy to come and look at it and he said the Mag. tube and the circuit bars were broken. Which would be more expensive to change the broken things or just...

He is referring to the magnatron tube which is the heart of the microwave. Probably more expense than you would want to put in to it.I would recommend replacement unless it is a high end model. Hope this helps

Jul 24, 2009 | Whirlpool MH7155XM Microwave Oven

1 Answer

Whirlpool MH7140XFQ-1 microwave no longer heating

Here is a tip that will help you to figure out what is wrong with yourMicrowave Oven....

Microwave Oven Basic Troubleshooting Tips


Apr 24, 2009 | Whirlpool MH7140XF Microwave Oven

1 Answer

Microwave not working

est the high voltage capacitor,the rectifier diode.or the magnetron. If all this are fine, test the control board.

Thediode and capacitors can br tested. The capacitor must bealloweddischarge before testing, or you risk to get electrocuted, evenifpower is off. Capacitors can get discharged by shorting theirtwocontacts.
Before replacing the magnetron test also the control board.
Replace the magnetron if the checks and all of the high voltage component tests are good, but the unit still does not heat.

All locations, and description of this parts can be located using the diagram here: Counter top.

Parts must be tested to find out what is wrong.

Remember that microwaves are potentially dangerous devices if not repaired properly, the job must be done by a competent person.
A microwave energy leakage test must always be performed when the oven is serviced for any reason.

Regarding parts, contact the seller here to purchase parts.

Dec 19, 2008 | Whirlpool MH7155XM Microwave Oven

1 Answer

Whirlpool microwave mh7140xfq

Curious, but did you know the diode was shorted without measuring it before you ordered the new one? I hope that's the problem.

In any case, there should also be a "mini-manual" (tech sheet) hidden inside the unit behind the control panel or hidden on the left side behind the grille, which is very helpful when troubleshooting & testing.

It usually has a perspective view drawing showing the relative locations of the components (parts layout).

If you don't have your tech sheet, you can find it online here and look on pages 3 & 4.

The diode (rectifier) is connected to one terminal of the high voltage capacitor and the other end goes to the chassis for ground.

It is located behind the magnetron in the back of the unit. You'll probably have to take the oven down from the wall to get to it safely.

Whirlpool customer service is here and you can also enter your model number on that page to download your owner's manual, installation instructions, etc.

Please read & heed the safety info in the tech sheet.

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

Oct 07, 2008 | Whirlpool MH7155XM Microwave Oven

1 Answer

Whirlpool microwave MH1170xsy0 1000 watts

With the symptoms you mention, I would suspect:

- loose or corroded connection at the magnetron
- bad magnetron
- shorted high voltage diode

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

There should also be a "mini-manual" hidden inside the unit behind the control panel or hidden on the left side behind the grille, which is very helpful when troubleshooting & testing.

Here are some links you or someone you know can use for test help, but read their safety warnings first:

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

Aug 20, 2008 | Whirlpool MH1170XS Microwave Oven

Not finding what you are looking for?
Whirlpool MH7140XF Microwave Oven Logo

104 people viewed this question

Ask a Question

Usually answered in minutes!

Top Whirlpool Microwave Ovens Experts

William Miller
William Miller

Level 3 Expert

9086 Answers

Donald DCruz
Donald DCruz

Level 3 Expert

17130 Answers


Level 2 Expert

228 Answers

Are you a Whirlpool Microwave Oven Expert? Answer questions, earn points and help others

Answer questions

Manuals & User Guides