Inside the oven cavity, usually on the right hand side or in the roof you will usually see a small cover that looks like it is made of cardboard. It is often held in by one or more screws.
What is it ?
It is called the waveguide cover. It is usually made of a material called Mica.
What does it do ?
Its purpose is to cover the aperture through which the microwaves enter the oven cavity from where they are produced by the Magnetron behind the control panel. It stops moisture and food particles getting into the “workings” of the microwave.
What do I need to know ?
if your microwave is working ok and behaving itself then there is nothing to worry about, but there may be one of 3 problems that may arise which should be rectified.
1. Its fallen off.
2. It has a hole in it.
3. It is arcing or sparking during use.
In any eventuality it should be replaced. If it has fallen off or got a hole in it then there is the risk of food or moisture getting into the waveguide which will reduce the efficiency of the oven. If it is arcing or sparking then continued use will damage other components in the microwave including the oven cavity which could be costly to rectify.
What should I do ?If there are any issues with your waveguide cover it should be replaced. When new the mica sheet is rigid and firm. Over a period of time it absorbs moisture and gets food splatters on it. It then becomes soft and flexible. The cover can be replaced either with a suitable replacement made by the manufacturer of the microwave or if the old cover is in good enough shape to be used as a template, blank sheets of mica can be purchased and cut to fit.
We often replace waveguide covers in our workshop. We are also asked to supply them directly. They are available mail order via our website ready made for some of the leading manufacturers or as blank sheets to make your own.