MT4078SPB1 Whirlpool Microwave - Instructions

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!

1. removed vent across the top to gain excess to Screw holding control in place. 2. Removed control panel to access Fuse. 3. Remover fuse after pulling plug. 4.Tested fuse for continuity with volt ohm meter noting no continuity.5. Orderd new fuse. 6. receeived new fuse and installed infuse holder.7. plugged microwave plug back in receptical and tested unit now working OK.Reversed steps 2 & 1 job complete

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.

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.

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.

Had a Trim Kit to remove, just 2 screws on the front to pull it out. Had to remove the tamperproof screws on the back (the outer shell is held on by them). I had to goto a local hardware store as nothing anywhere mentioned I needed this special tool (NOTE!!!!!!!) The bottom had normal phillips head screws. Note: I did not take the entire shell off, just bent it enough so the base plate could be pulled out. This exposed the motor, which strangely enough is NOT held in by any screws, just notches it slides in. Took the old motor out, came out VERY easily (only 1 plug to pull out). The new motors flange tab was bent a little bit so I had to use pliers to bend it back flat so it would fit in the notch on the bottom of the microwave (very easy). Overall A bit difficult due to special tool needed 9at least for me)

I could just set the new whirly gig in the bottom hole of the micro and it worked. The new part was delivered in 24 hours of my order and hence fixed in 24 hours. Thanks so much Part Select

Took the cover off, had a lot of screws but easy. Removed the old motor and inserted the new motor. Replace the metal cover and it was ready to go. Can't believe I have waited so long to do this. I was going to replace the microwave but could not find the correct size to fit the cabinet.

Watched a you tube video prior to installing new switch. Followed the video which gave me confidence i was up to the task. After removing the touch pad I found my design was not exactly like the you tube model but I found the defective switch, replaced it and put the microwave back together. Works great. Again watch the videos

It seems that the heat of the microwave cracks the part over time. It is a very simple installation.

Using fingers, the old turntable roller guide was pulled up off the motor shaft. The plastic roller guide shaft coupler was found to be broken, allowing the motor shaft to spin without turning the roller guide. The hole in the floor of the oven was inspected, and no broken pieces were found which could interfere with the new roller guide. The new roller guide was then gently pressed down over the motor shaft. Very easy.

took out plastic piece under plate (that was broken) and placed new one in the hole. No tools req'd. Works like new.

Ice covered the top back of the freezer compartment. This did not allow the cold air to move up to the fridge. Complete defrosting (36hrs) fixed the problem. There was a lot of water, from ice inside, that was not visible. We realized the freezer drawer must have been left cracked open. Thanks so much.

Replaced the diode (aka wire-vltge) in the HV circuit after removing cabinet cover using both the secure torx screw drvr & phillips head screw drvr. The hardest part of the job was finding the secure torx nut drvr tool on the internet & purchasing same.

All the electrics worked on Amana microwave EXCEPT for the cooking function. Inspected the control board and found the upper switch on the door interlock was burnt. Installed new switch in minutes and everything now works fine. Unfortunately, had to purchase expensive two switch "kit" although only one switch was kaput. PartsSelect mailing was SUPER fast. Thanks for looking, Scott