ACM1420AB - Overview

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!

My 8 year old daughter cleaned the inside of the microwave with enough water to rival a tsunami. Resulted in a clean microwave with a fried out motor that no longer revolved. Part came quickly. Took cover and bottom off to get to the part. One screw held it on and a plug. Removed those, put on new part and she was good to go. No trip to home depot today.