Microwave runs but does not heat; display shows E3 after a few seconds.

Safety Warning: The high-voltage section of a microwave is extremely dangerous. The capacitor can store a lethal charge even when unplugged. High-voltage troubleshooting and parts replacement should be done only by qualified technicians.

User-level checks:

• 1. Confirm symptom: Place a cup of water in the oven and run on HIGH for 1–2 minutes. If the turntable rotates and the light is on but the water remains cold and E3 appears, the high-voltage system is likely at fault.
• 2. Power reset: Unplug the microwave for 5–10 minutes, then plug back in and test again. If E3 returns, internal components need service.

Technician-level overview (for reference only):

• 3. Inspect high-voltage components: With the unit unplugged and the capacitor safely discharged, a technician will visually inspect the high-voltage transformer, capacitor, diode, and magnetron for burn marks, bulging, or cracks.
• 4. Test continuity: The transformer primary and secondary windings, capacitor, and diode are tested with a meter. Any open or shorted component is replaced with an RCA-compatible part.
• 5. Verify operation: After replacement, the technician will reassemble the unit, perform a leakage test, and confirm proper heating.

If you are not trained in microwave high-voltage repair, discontinue use and contact an authorized RCA service provider.