Microwave will not start; display shows E1 immediately after pressing START.

Safety first: Unplug the microwave before any disassembly. High-voltage components inside a microwave can retain a dangerous charge even when unplugged. Do not touch the capacitor or magnetron area unless you are trained.

Step-by-step checks:

• 1. Inspect the door closure: Ensure the door closes fully and evenly. Check that the latch hooks on the door are not cracked or bent and that the door is not sagging on its hinges.
• 2. Test door switches (interlock switches): Remove the outer cabinet (usually screws on the back and sides). Locate the door switch bracket near the latch area. You will typically find a primary, secondary, and sometimes a monitor switch. Using a multimeter set to continuity, test each switch while pressing and releasing the door button. Replace any switch that does not change state (open/closed) correctly.
• 3. Check switch bracket and alignment: Verify the plastic or metal switch bracket is not cracked or loose. If the bracket is misaligned, the door hooks may not fully actuate the switches. Tighten mounting screws or replace the bracket if damaged.
• 4. Inspect wiring harness: Check the wiring to each door switch for burned connectors, loose terminals, or broken wires. Repair or replace damaged wiring using proper crimp connectors and high-temperature-rated wire.
• 5. Reassemble and test: Reinstall the cabinet, plug in the microwave, and test operation. If E1 persists, discontinue use and contact a qualified technician, as the control board may also be involved.