Microwave does not start; display is on, but pressing START does nothing or beeps and returns to clock.

Safety first: Unplug the microwave from the mains before removing any panels. Never operate a microwave with the cover removed. Do not touch the high-voltage capacitor or magnetron area unless you are trained and have discharged the capacitor properly.

Step-by-step checks:

• 1. Inspect the door and latches: Open and close the door firmly. Check that the plastic latch hooks on the door are not cracked or loose and that the door sits evenly in the frame on your Grundig microwave.
• 2. Listen for switch clicks: Slowly open and close the door while listening for 2–3 distinct clicks from the interlock switches. Missing clicks can indicate a failed or misaligned switch.
• 3. Access the door switch assembly: Remove the outer cabinet (usually screws at the back and sides). Carefully slide the cover back and up. Locate the door interlock switch cluster near the door latch openings.
• 4. Test the switches: With a multimeter set to continuity, remove one wire at a time from each switch. Check that the primary and secondary switches change from open to closed when the door is operated. Replace any switch that does not change state correctly.
• 5. Check the mounting bracket: Ensure the metal or plastic switch bracket is not bent or cracked. If it moves when the door is opened/closed, the switches may not actuate fully and the control board will trigger E01.
• 6. Reassemble and test: Refit the cabinet, plug the unit back in, and test with a short 30-second heat cycle in a microwave-safe cup of water.

If the error persists after replacing faulty switches, the control PCB may be misreading the interlock circuit and should be checked by a qualified technician.