Digital Reliance water heater display shows E0 and unit will not heat water

Safety first: Turn OFF power at the breaker (electric) or set gas control to OFF and unplug power cord (gas/electric hybrid). Verify power is off with a non-contact voltage tester before touching wiring.

Steps to check:

• 1. Power cycle: Turn power off for 5 minutes, then restore power. If E0 clears and does not return, it may have been a transient communication error.
• 2. Inspect control wiring: Remove the front access panel. Locate the low-voltage harness between the display/user interface and the main control board. Check for loose plugs, bent pins, corrosion, or moisture. Reseat each connector firmly.
• 3. Check for damage: Look for burn marks, melted plastic, or rodent damage on the harness. If any conductor is cut or insulation is missing, replace the harness.
• 4. Test continuity (advanced): With power still OFF, disconnect the harness at both ends and use a multimeter to check continuity on each conductor. Any open circuit indicates a bad harness.
• 5. Replace suspect board: If wiring is good and E0 persists, the fault is usually in the main control board. Replace the main control board with the exact Reliance part number for your model. If still unresolved, replace the user interface/display board.

When to call a professional: If you are not comfortable working around live circuits or cannot identify the correct replacement board, contact a qualified water heater technician.