Have a whirlpool MH3184XPS-3 and need a shematic wiring diagram

A dead short---most have a large diode inside that you may have by accident destroyed. I will attach a photo of a typical diode but yours likely will be similar or may look different---it will have the diode symbol on it and or a band at one end---it has to go the same direction as the one in the unit.

Simple to test with a meter--resistance reading should NOT read like a fuse.



note the triangle shape on this one

On this model, this is usually a blown fuse or thermostat.

This model has three fuses, a 20A, a 4A, and a .25A and three cavity thermostats.

There should 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, and locating components.

At our Web site, we have a video available showing how to remove a typical over the range control panel assembly in under 5 minutes.

Accessing the cavity thermostats for testing and possible replacement will require you to remove the oven from the wall.

If so, the installation instructions are very handy, and it's best to have two people since the microwave can be heavy and awkward.

If for some reason you don't still have yours, you can download Whirlpool owner's manuals and installation instructions here.

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

If none of the fuses or thermostats are blown, then the problem is probably on your control circuit board, which is especially common if you recently had trouble with your cooktop lights or exhaust fans.

We see (and repair) this a lot. The problem is on the control panel, which we regularly repair nationwide by mail for $39.95 postpaid with a one year guarantee.

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

Hi and welcome to FixYa, I am Kelly.

When a microwave suddenly quits and causes the internal FUSE to open it is usually either the high voltage power diode or the high voltage capacitor that has failed causing the fuse to fail. After searching for your model number it appears that this is a Canadian model. LG does not have many parts for this unit listed on their website at all. All but 2 of the items the sell are "out of stock." Neither the diode or the capacitor are are listed. These parts can be replaced with GENERIC equivalent parts.

• First off unplug the unit.
• Remove the outer chassis cover ( 6 screws in the back and 4 on the sides )
• Hold a screwdriver way back on the handle and short across the high voltage capacitor at least 3 times (Will really ruin your day if it is good and still has a charge!) This may make a huge BANG / Blue Spark. Not to worry it is normal and your using the screwdriver to discharge the capacitor.
• Note installed wire positions (make a sketch) and remove all the wires off one side of the capacitor.
• Use a meter set on R X 10,000 and probe across the capacitor terminals. You should see a momentary jump in resistance then the meter returns to infinity. Reverse the meter leads (polarity) and probe the terminals again. Watch for a momentary jump in resistance and the peter returns to infinity. (no momentary jump = bad capacitor)
• Next test the power diode by reading resistance in BOTH directions (reversing leads / polarity) Is should only read resistance like a wire in ONE direction and be OPEN in the other. (Resistance in both directions or no resistance at all = bad power diode)
• After you have located and replaced the bad component REPLACE THE FUSE that will be in the fuse block at the end of the main power cord wire. Just follow the cord to the fuse block. The fuse will either be a 15 or 20 Amp Slo-blow fuse.
• Install the outer chassis cover and test.

Those are the 3 most common reasons that the unit stops working while in use. i.e Capacitor, Diode and Fuse. There are other things that can cause it: Magnetron, Controller and the Door Interlock Switch but I would try the above and I am pretty sure you can bring it back to life. Either way unless you just want a new microwave a repair tech is going to do exactly as I stated.

If you need more assistance feel free to respond here with any questions or concerns. I will gladly help you.

Thanks for choosing FixYa,
Kelly

All of your measurements sound good, quite possibly bad mag.

Hi and welcome to FixYa. I am Kelly.

Most of the time when the microwave is in use and just quits either the Power Diode or the capacitor has failed and blows the fuse inside the cabinet. (Yours is probably NOT blown.)

Diode:
http://www.appliancepartspros.com/part_details.aspx?part_id=4310285

Location Item 19
http://www.appliancepartspros.com/partsearch/model.aspx?model_id=260502&diagram_id=94048#d94048

Capacitor: (Location Item 20 above link)
http://www.appliancepartspros.com/part_details.aspx?part_id=4295779
Since you unplugged the unit before the thermal fuse blew you were very wise: (Item 28 of interior diagram)
http://www.appliancepartspros.com/part_details.aspx?part_id=4308182


With the unit unplugged and the chassis cover removed the fuse will be located at the end of the power cord lead in a fuse holder. The fuse is usually a 15A 250V slow-blo fuse. Just replacing the fuse will normally result in the fuse failing yet again.

STOP! Before going any further you must hold a well insulated screwdriver back on the handle and short across the High Voltage Capacitor at least 3 times! Failure to do so could be the start of a very bad day in the form of a horrible shock.

Next you disconnect one side of the cap including the power diode wire. With an analog meter set on R x 1,000 read the Cap terminals watching for a jump. Reverse the meter leads on the terminals and watch for a jump EACH time you reverse the test leads on the CAP terminals.

No jump = bad cap.
Constant resistance across the cap = bad cap

Lastly you check the power diode with the meter on the same settings R X 1,000. One direction will read full continuity (ZERO) and reversing the leads will read infinity. (no reading)

If the diode reads open both ways = failed
If the diode reads (ZERO) both ways = failed
It must read continuity in ONE direction only.

After finding and replacing the failed component then you can change the fuse and test the microwave.

There is a very very remote possibility that a door switch has failed but given that your microwave failed while in use I seriously doubt you have a door switch problem.

As far as finding replacement parts for your microwave nearly every appliance parts store will have what you need if you walk in with the failed part in hand. Most of the time they will walk back and grab the part you need without even digging in the parts books.
These are the most common failures when a unit quits working while in use. Yes I believe your unit is repairble at a very reasonable cost.

Thanks for choosing FixYa.

Kelly

logic board needs replacement if it cannot be reset.

This means the magnetron is either bad, is not receiving the high voltage it needs (failed diode) and/or the fuse is blown.
You can trouble shoot this yourself with the help of a cheap digital multimeter and a reading of the Chinglish instructions that come with it.
Be advised though; if the magnetron and the diode are OK you can encounter ~ 700 volts on a charged capacitor so let the unit rest unplugged overnight if you intend to poke around in it.

My Whirlpool MH3184xps is shooting a spark when in use with the rack. When the rack is removed the oven works fine. I am guessing that some of the coating on the rack has cracked and peeled and is exposing some aluminum. Has anyone else had this problem?

First change all the fuse and check whether it works or not, if it does not work than as per your finding the secondary transformer could be the issue, the secondary transformer tap down the voltage fro 230-240/110 to required control board voltage. the best thing if the unit is opened then the right problem can be found but as per your description either fuses are faulty or the secondary transformer.

Our GE jvm1870 is now over 4 yrs old, and had been working fine-- until recently when using, didn't heat anymore & also started making a crazy sound.

Am no electrician, so I called GE to help. Needed a new magnetron & some diode. Part was under a 10 yr warranty- the total cost for service call + labor was under $200. Not great, but beats buying a new microwave ($400-700) and having to install it.