How to Troubleshoot & Replace Whirlpool AP6009302 / WP4375424 Magnetron (Microwave)

Pulled out oven and microwave combo from the cabinetry. Remove side rails in the front. Remove oven door for ease of movement. Be sure to support oven well. Carefully remove cover of microwave on right hand side (will need a small torx driver to remove screws on inner cover). Discharge capacitor with well insulated screw driver (DO NOT DO IF YOU DON'T KNOW WHAT YOU ARE DOING). Need another torx driver, slightly larger, to remove the magnetron. Magnetron easy to remove and install but time consuming to get to. Fixed the problem. 

I measured the resistance between the two connectors on the magnetron: should be close to zero ohms and it was. I measured between the same connectors and the metal case: should be mega ohms, it was 15k ohms. That is a bad, partly shorted unit. I also checked the resistance of the thermal cut off, which should be zero but was 10 ohms so I replaced. The HV diode is checked with a 9 V battery (YouTube checking microwave HV diode) and it too was bad. Make sure to take pictures as you disassemble the unit as I had a few leftover screws. Unit is working great now. 

Replaced Magnetron and Diode. The Diode was still good, but while in there it seemed like a good investment to replace it. 

I electrically tested the magnetron, diode and capacitor and determined both magnetron and diode were defective. Ordered replacement parts late on Friday (unfortunately Monday was Memorial Day) and order wasn't processed until Tues. Regardless, I received parts a little after noon on Thursday in upstate NY. Installed parts on Friday and microwave has a new lease on life. Job well done by AppliancePartsPros!! Repair was complicated a bit as the KitchenAid microwave doubles as a convection oven and is mounted in a double convection oven stack. 

Replaced the magnetron, diode, and a light bulb. 

I figured this was probably the magnetron -- And a little reading on line reinforced that. Ordered replacement magnetron and diode, as well as door torsion springs on a separate order (might as well get it all done while the box is open). While there are a lot of pieces to remove and screws to keep track of, the repair was simple and didn't take long. Just be sure you discharge your capacitor so you don't light your head on fire. 

Bought a magnetron and a diode. Spent 2 hours putting it in and voila, it works as good as it did when we first bought it 15 years ago. It is a convection oven so it would have cost us $2000 for a new one. Thank you 

Replaced the Magnetron and Diode.