Frigidaire microwave keeps blowing fuses.

Hi @movaska978

Use a DMM (digital multimeter) to test the door interlock switches that you have already replaced to see if any test short circuit regardless of being operated or released.

The primary and secondary interlock switches should test open circuit at normal (N.O. switch) and short circuit i.e. 0.00 Ohms when they're operated and the monitor switch should test short circuit at normal (N.C. switch) and open circuit when it's operated.

If any switch tests short circuit when it is both operated and released, this means that the switch contacts have fused together.

This is usually caused by:

a). user misuse. The user opens the door when the oven is operating to stop it, instead of using the control panel's stop button to stop it and then opening the door. If done often enough, over time this causes door switch contact surface migration due to current flashover i.e. spark across switch contacts, that eventually welds the contacts together.

b). loose or worn latch hook switch holder. The switches should operate/release in a set order so as to prevent all three switches being in the closed position at the same time. The monitor switch should open just before the other two switches close when the door is being closed and close just after the other two switches have opened when the door is being opened.

c). Poor quality switches. The cheaper switches tend to fail a lot sooner than more expensive ones if user misuse as described above occurs often. You get what to pay for, I suppose. The part number for the monitor switch is 5304509459 and the primary and secondary switches is 5304509460