Check the power source that the microwave is plugged into before beginning the repair process. If the microwave display is found to be defective, search online or visit a home appliance store to price the parts that will be needed to fix the display. The Repair FAQ website explains that unless the microwave isn't very old, purchasing a new microwave can be less expensive than fixing the old one. Depending on your model, you might need to replace an entire side-panel component, which as of December 2010 will cost you around $100.
Use a screwdriver to loosen and remove the microwave from the kitchen unit. After the microwave is placed on a secure surface, remove the panels to access the inner components. You'll need to thoroughly inspect the parts to determine why the display isn't working.
Locate the various fuses within the microwave to determine whether they need replacing. The Microwave Wizard website explains that the temperature and monitor fuses can affect the microwave's display. Examine whether the fuse is discolored or if the filament is broken.
Purchase new fuses and install them in the microwave as needed. The Microwave Wizard website explains that the individual should also check the circuit board within the microwave to determine whether any lines or digits are missing. The display issue can be related to missing solder in the circuit board.
Check the circuit board thoroughly to locate the broken line. Use the soldering iron to solder the line back into place. After replacing or fixing the fuses and lines, test the microwave display to ensure that it is working correctly.