MMV6178AAS - Instructions

1. I went to the internet to find the service manual for the Maytag microwave.
2. I opened up the oven and started measuring the resistance of the diode, capacitor, transformer, and magnetron between terminals and then to ground. The transformer and magnetron were well within the resistance limits. The diode was shorted in both directions(+-). The capacitor was fully open in both directions -- high resistance.
3. I ordered the 2 parts, installed them, and ran the oven. Worked perfect first time.
4. Reinstalled oven and worked ever since (1 week so far).
5. The secret was that the transformer had a load hum. I figured the transformer was OK. The magnetron had no short between filaments and ground to filaments. The only two left were the diode and capacitor. The first two are about $200 -- almost the value of a new microwave. The $70 repair was well worth it. If the first two were still bad, then tempted to buy a new oven.

Remove top grille (2 screws), undo control panel (1 screw). Tilt down control panel, switches are on the left. There are actually three switches that are involved with the door, two horizontally mounted, one vertically mounted. This would be an EASY REPAIR, but it took me a while to figure out which of the three switches was bad, and also took a while to figure out that there is a plastic rod that inserts through the hole in the switch body. Once i figured this out went like a breeze. Lower horizontal switch was the bad one, but since the kit came with two switches i went ahead and replaced the upper horizontal one as well. IT appears that the horizontal switches are probably more likely to fail than the vertical switch based on the position of the switch and force angles. Works great now!

I looked up the #1 reason for no heat for my microwave on the site , and using my model number found that 92% of the time it was the Black Sleeve Diode. Ordered the $15 part, and installed it within 30 minutes. Most of the time was used for removing the built in microwave and removing the cover. Replaced the diode by finding it on the diagram that I printed from this site (free). Very relieved that we don't need to have our custom cabinetry re-sized to accommodate a new microwave. Thank you!

Unplug the unit before servicing. Need phillips screwdriver. Open door. Use step ladder to access and remove 2 small screws from top of the room air diffuser at top of unit. Slide diffuser slightly to the left to align the diffuser's plastic tab on the left side to rotate toward you. (The wires for the front control panel are at the far left side of this difuser, but difuser is slotted for easy removal). Once the difuser is removed you will see 1 screw at the top that secures the pannel cover on the left side of the unit. Remove screw and slide this panel slightly up and out. This exposes the plastic frame that holds the upper and lower door switches. To locate the door switches and observe how they work, close and open the door and watch the door (bayonets) open and close the micro switches. Do the (red) buttons on top of the switches move up and down when the door bayonets push and release? If the buttons do not "pop" up when opened the switch is defective. The switch frame is secured with 2 screws. Remove screws and rotate the unit out for easy access to the micro switch(s). The internal (spring?) on my unit that is suposed to allow the red (visible) button on top of the switch to "pop" up when the door is opened was broken. Carefully pry the switch outward while being careful to lift the plastic holder-piece that holds the switch in place. Be careful, there is a small pin on the frame, so rotate the switch OUT toward you while lifting (carefully) the plastic holder-piece (you will see it on top of the switch). You can use an ohm meter to test the continuity of the switches. But if the buttons don't "pop" they are defective. Replace switch and reassemble.

Bought new plate.

I removed the unit from the wall. Took the cover off. Set the unit on its side. It revealed the working parts. Removed the old micro switches. Put in the new oness. Presto, it worked. Very easy for me.
The parts was delivered almost before my notice they were shipped.

Once I got the replacement bulb, the repair was
easy. I needed to unscrew one side of the lamp assembly and pop the new bul in.

My problem was getting the right light. The local hardware store didn't carry quite the right halogen lamp and the one I bought burned out the wires that hold the light. THis was a costly repair --- about $100. So I was delighted when Part Select had the lamp I needed. They were prompt in sending it out and I was very satisfied.

removed various screws on tp, bottom and back to remove cover. Thermostat is behind control panel held in with metal tabs. Just bend the tabs straight and remove, install new thermostat in reverse order.

removed the cover with a phillips screwdriver and replaced filter

1. Removed cabinet screws (10-15?). 2. Removed cabinet. 3. Removed top interlock switch which actually was not defective. The press clip connection appeared as if it had been arcing for quite some time and the corrosion created resistance sufficient to prevent the current from getting through the switch. 4. Replaced switch anyway but broke plastic retaining clip despite every effort not to do so. Reset broken clip with super glue. 5. Reassembled cabinet and appliance is in good working condition.

Problem would come and go. Found service schematic inside unit. Perform all the suggested tests. One possible solution was the primary interlock switch shown on the schematic and a check found the switch stuck. It would free up some times but would stick again in the open position. Ordered switch which was a simple plug in unit.

Watched a couple of repair videos on Youtube by searching for the model number. Found out what to do in order not to get shocked by the powerful capacitor.
Ordered the two switches (To be sure, I could have ordered a third switch as suggested in the videos.)
Bought a tamper-proof star bit to get the cover off. Followed the directions to replace the switches. - I broke the harness and had to use some super glue, but it's all good. I should have removed the harness instead of trying to get a switch out while it was still in place.
It's all back together, and the wife is happy!!

I unplugged the microwave. I did watch a YouTube video to see how the plastic frame around the door could be removed. I used a putty knife to pry it off. The spring was still in good shape, so I hooked it up to the new latch/locker part and onto the microwave. This was just a little time consuming because I was trying to be careful so I wouldn't break anything on the new part. The plastic frame clicked right back on. I plugged the microwave in and it worked right away. If I can do it, you can do it. Sure beat buying a new microwave. Great experience.

Removed case,
Discharged HV capacitor and removed cooling fan.
Unscrewed ground end of HV diode and unplugged from HV capacitor.
Installed new diode by reversing the order. In my case, the problem was the magnetron was bad, so I replaced it as well.

Removed some cosmetic panels. Removed the assembly with micro switches. Examined the faulty switch by checking the clicking action of switch. Two others were ok by this method. Replaced the switch with new one. Works fine so far. Thanks to web site and YouTube videos.