Electronic Control Board WPW10486188

Hired a contractor to perform the repair. He didn't show up. Went to Lowes, where the item was purchased, and they didn't know anyone who serviced the unit or where to find a technical manual. Built a platform to hold the unit and my wife and I isolated the power, verified no current, and slid the unit out of the wall to see what was involved.

Found the technical manual in a pouch on the side of the oven and went through the checklist. Found through online research that about 60% of the failures were the inverter, 30% were the Control Board, and 10 or so % were the Magnetron. Made the mistake of getting parts based upon failure rate rather than having someone technically qualified perform a detailed diagnosis. So, after replacing the high frequency failure parts without success, got a well- qualified technical electronics person to help. He did the diagnosis and determined that the problem was in the magnetron unit and was probably the "Thermister." The Thermister is the absolute cheapest part of the four involved with the exception of the high voltage diode, which is on one of the boards already replaced.

The Thermister is probably the part needed since it is on backorder for a couple of weeks by all the online parts suppliers checked.

At this point, we will replace the Thermister and return the Magnetron if that works. If not we will replace the Magnetron. When that is done we will have completely rebuilt the unit and it should be good for another 4 or five years.

The repairs are relatively easy. The boards are static sensitive and both the main board and replacement parts need grounded. There is also a capacitor that needs to be discharged before working on the unit. Total weight of the combo unit is about 70 pounds but it is bulky so a helper to lift the unit down to work on the microwave is necessary to safely remove the built in unit and to replace it.

Some lessons learned:
1. Combo oven units do not have separate ovens and microwave components.
2. When the power is off on the oven combo unit, all of our electric cooking appliances were out of service - including the glass cooktop.
3. Cost of the individual cookiing units - oven, microwave - is much less than the cost of the combination unit.
4. Ovens have a 20 year life expectancy, microwaves have a 5 year life expectancy. Therefore, think carefully about the combo unit vs individual units during construction.
5. There is a screw behind the wiring harness that cannot be accessed with the nut driver very well. This holds the cover on. An 8mm wrench worked well to remove this.
6. Parts described in the manual are not the same as part nomenclature on the online repair manuals or parts listings, nor are part numbers the same.
7. PartSelect.com verified the part nomenclature and identified their part number for the components listed in the Service Manual with the combo unit. I cannot speak highly enough for the assistance and support we received from them while ordering parts.
8. The most difficult part of this entire operation, now in week 4, is finding the service manual, identification of the defective part, and obtaining the parts. (Paying for them is not a joy either.)

Recommendations:
1. Get a well qualified electronic person to help identify breakers which need isolated, go through the diagnostics, and accurately identify the part needed before buying any parts.
2. Plan to be without all connected appliances while the oven combo is locked out of the breaker panel
3. When building a new home have the built in oven and microwave installed in separate cabinets and wired separately with individual power and control circuits.

All the best in your repairs.

Mike